Update devDependencies, fix eslint, use ES6

[afshin]

This PR:

• Updates to ES6 everywhere
• Updates to lerna
• Fixes eslint errors and warnings
• Updates rollup
• Updates webpack

With this PR

$ eslint --ext .js,.jsx,.ts,.tsx --cache --fix .
✨  Done in 1.57s.

Before this PR

$ eslint --ext .js,.jsx,.ts,.tsx --cache --fix .
=============

WARNING: You are currently running a version of TypeScript which is not officially supported by @typescript-eslint/typescript-estree.

You may find that it works just fine, or you may not.

SUPPORTED TYPESCRIPT VERSIONS: >=3.3.1 <4.2.0

YOUR TYPESCRIPT VERSION: 4.7.4

Please only submit bug reports when using the officially supported version.

=============

/Users/af/Code/lumino/packages/datagrid/src/celleditor.ts
   832:3   warning  Missing return type on function                       @typescript-eslint/explicit-module-boundary-types
   845:25  warning  Argument 'value' should be typed with a non-any type  @typescript-eslint/explicit-module-boundary-types
   853:3   warning  Missing return type on function                       @typescript-eslint/explicit-module-boundary-types
   863:3   warning  Missing return type on function                       @typescript-eslint/explicit-module-boundary-types
   934:3   warning  Missing return type on function                       @typescript-eslint/explicit-module-boundary-types
   985:3   warning  Missing return type on function                       @typescript-eslint/explicit-module-boundary-types
  1052:3   warning  Missing return type on function                       @typescript-eslint/explicit-module-boundary-types
  1065:3   warning  Missing return type on function                       @typescript-eslint/explicit-module-boundary-types
  1174:3   warning  Missing return type on function                       @typescript-eslint/explicit-module-boundary-types
  1187:3   warning  Missing return type on function                       @typescript-eslint/explicit-module-boundary-types
  1280:3   warning  Missing return type on function                       @typescript-eslint/explicit-module-boundary-types
  1295:3   warning  Missing return type on function                       @typescript-eslint/explicit-module-boundary-types
  1466:3   warning  Missing return type on function                       @typescript-eslint/explicit-module-boundary-types
  1479:3   warning  Missing return type on function                       @typescript-eslint/explicit-module-boundary-types

/Users/af/Code/lumino/packages/datagrid/src/celleditorcontroller.ts
  119:3  warning  Missing return type on function  @typescript-eslint/explicit-module-boundary-types

/Users/af/Code/lumino/packages/datagrid/src/datamodel.ts
  153:5  warning  Argument 'value' should be typed with a non-any type  @typescript-eslint/explicit-module-boundary-types

/Users/af/Code/lumino/packages/datagrid/src/graphicscontext.ts
   93:20  warning  'CanvasTextAlign' is not defined           no-undef
   97:24  warning  'CanvasTextAlign' is not defined           no-undef
  104:23  warning  'CanvasTextBaseline' is not defined        no-undef
  108:27  warning  'CanvasTextBaseline' is not defined        no-undef
  115:18  warning  'CanvasLineCap' is not defined             no-undef
  119:22  warning  'CanvasLineCap' is not defined             no-undef
  137:19  warning  'CanvasLineJoin' is not defined            no-undef
  141:23  warning  'CanvasLineJoin' is not defined            no-undef
  236:35  warning  'GlobalCompositeOperation' is not defined  no-undef
  240:39  warning  'GlobalCompositeOperation' is not defined  no-undef
  318:50  warning  'CanvasFillRule' is not defined            no-undef
  408:19  warning  'CanvasFillRule' is not defined            no-undef
  416:19  warning  'CanvasFillRule' is not defined            no-undef
  489:3   warning  Missing return type on function            @typescript-eslint/explicit-module-boundary-types

/Users/af/Code/lumino/packages/domutils/src/selector.ts
  117:32  warning  Don't use `Function` as a type. The `Function` type accepts any function-like value.
It provides no type safety when calling the function, which can be a common source of bugs.
It also accepts things like class declarations, which will throw at runtime as they will not be called with `new`.
If you are expecting the function to accept certain arguments, you should explicitly define the function shape  @typescript-eslint/ban-types

/Users/af/Code/lumino/packages/properties/src/index.ts
  225:29  warning  Argument 'owner' should be typed with a non-any type  @typescript-eslint/explicit-module-boundary-types
  261:29  warning  Argument 'owner' should be typed with a non-any type  @typescript-eslint/explicit-module-boundary-types

/Users/af/Code/lumino/packages/signaling/src/index.ts
  150:29  warning  Argument 'thisArg' should be typed with a non-any type        @typescript-eslint/explicit-module-boundary-types
  164:32  warning  Argument 'thisArg' should be typed with a non-any type        @typescript-eslint/explicit-module-boundary-types
  199:37  warning  Argument 'sender' should be typed with a non-any type         @typescript-eslint/explicit-module-boundary-types
  199:50  warning  Argument 'receiver' should be typed with a non-any type       @typescript-eslint/explicit-module-boundary-types
  208:36  warning  Argument 'sender' should be typed with a non-any type         @typescript-eslint/explicit-module-boundary-types
  222:38  warning  Argument 'receiver' should be typed with a non-any type       @typescript-eslint/explicit-module-boundary-types
  236:33  warning  Argument 'object' should be typed with a non-any type         @typescript-eslint/explicit-module-boundary-types
  249:29  warning  Argument 'object' should be typed with a non-any type         @typescript-eslint/explicit-module-boundary-types
  315:5   warning  Argument 'thisArg' should be typed with a non-any type        @typescript-eslint/explicit-module-boundary-types
  366:5   warning  Argument 'thisArg' should be typed with a non-any type        @typescript-eslint/explicit-module-boundary-types
  405:37  warning  Argument 'sender' should be typed with a non-any type         @typescript-eslint/explicit-module-boundary-types
  405:50  warning  Argument 'receiver' should be typed with a non-any type       @typescript-eslint/explicit-module-boundary-types
  441:36  warning  Argument 'sender' should be typed with a non-any type         @typescript-eslint/explicit-module-boundary-types
  474:38  warning  Argument 'receiver' should be typed with a non-any type       @typescript-eslint/explicit-module-boundary-types
  507:33  warning  Argument 'object' should be typed with a non-any type         @typescript-eslint/explicit-module-boundary-types
  585:5   warning  Do not use "@ts-ignore" because it alters compilation errors  @typescript-eslint/ban-ts-comment

/Users/af/Code/lumino/packages/widgets/src/docklayout.ts
  2084:10  warning  Missing return type on function  @typescript-eslint/explicit-module-boundary-types
  2097:10  warning  Missing return type on function  @typescript-eslint/explicit-module-boundary-types

/Users/af/Code/lumino/packages/widgets/src/dockpanel.ts
  880:9  warning  Unexpected lexical declaration in case block  no-case-declarations

/Users/af/Code/lumino/packages/widgets/src/tabbar.ts
  1776:18  warning  'ClientRect' is not defined  no-undef

/Users/af/Code/lumino/packages/widgets/src/widget.ts
  778:17  warning  'HTMLElementTagNameMap' is not defined  no-undef

/Users/af/Code/lumino/scripts/format-changelog.js
  6:7  warning  'package' is assigned a value but never used  @typescript-eslint/no-unused-vars

✖ 55 problems (0 errors, 55 warnings)

✨  Done in 6.60s.

cf. #325

[fcollonval]

Thanks a lot @afshin

I got a few suggestions.

[fcollonval]

🎉 we should definitely bring that to JLab

[fcollonval]

It is probably out of scope for this PR. But it will be nice to drop webpack because it is inconsistent to distribute lumino using rollup but testing it using webpack.