Extend eslint-rules

[narickmann]

In Studio we already use eslint-config with few rules.
To keep the code readable, nice, and consistent, I would like to add a few more rules.
I looked at the eslint rules and picked out a few that I think are useful.

Feedback and further suggestions on the rules are of course welcome.

I would like to implement these rules:

• "arrow-spacing": "error"
  -> Enforce spacing before and after the arrow in arrow functions
• "brace-style": "error"
  -> Enforce consistent brace style for blocks
• "comma-spacing": ["error", { "before": false, "after": true }]
  -> Enforces consistent spacing after commas in variable declarations, array literals, object literals, function parameters, and sequences
• "eol-last": ["error", "always"]
  -> Enforces that files end with a newline (LF)
• "func-call-spacing": ["error", "never"]
  -> Disallows spaces between the function name and the opening parenthesis that calls it
• "indent": ["error", 2]
  -> Enforce consistent indentation
• "linebreak-style": ["error", "unix"]
  -> Enforce consistent linebreak style
• "max-len": ["error", { "code": 120, "ignoreUrls": true }]
  -> Enforce a maximum line length
• "no-multi-spaces": ["warn", { "ignoreEOLComments": true }]
  -> Disallow multiple whitespaces around logical expressions, conditional expressions, declarations, array elements, object properties, sequences and function parameters
• "no-trailing-spaces": "error"
  -> Disallow trailing whitespace (spaces, tabs, and other Unicode whitespace characters) at the end of lines
• "object-curly-spacing": ["error", "always"]
  -> Enforce consistent spacing inside braces of object literals, destructuring assignments, and import/export specifiers
• "semi": ["error", "always"]
  -> Require semicolons at the end of statements
• "space-before-function-paren": ["error", "never"]
  -> Disallow spacing before function parentheses
• "space-infix-ops": "error"
  -> Require spacing around operators

I'm not quite sure if these rules are too much:

• "array-bracket-spacing": ["error", "always"]
  -> Enforces consistent spacing inside array brackets
• "arrow-parens": ["error", "as-needed"]
  -> Enforces parentheses around arrow function parameters as-needed
• "jsx-quotes": ["error", "prefer-double"] or "jsx-quotes": ["error", "prefer-single"]
  -> Enforce the consistent use of either double or single quotes in JSX attributes

[lkiesow]

All suggested rules sound reasonable to me. No objections.

The only thing I would look out for is if one of the rules requires changing a lot of code. That can be annoying not only because you have to do the reformatting, but also because that means you cannot any longer easily find out why a given line was changed (last commit). Or rather, the reason will then always be formatting, which isn't helpful. If that is the case I would consider if it is worth applying that specific rule. But I don't think that will be a problem for most of these.

I like having these things checked automatically!

[narickmann]

I also want to add: "block-spacing": ["error", "always"] (Enforces consistent spacing inside an open block token and the next token on the same line).

Not sure if we want "array-bracket-spacing": ["error", "always"]
Every useState declaration will look like this: const [ state, setState ] = useState() I'm not quite sure, if I like how it looks now.