[No ticket][TypeScript] Update publishing setup

[mschuwalow]

Updates our packaging setup to have a more modern / best practices setup.
After this is merged we will stop emitting the cjs + esm (which is a backwards compat breaking change / we will have one anyway unless we want to generate a fake 'src' folder from typescript).

Instead the following files are created:

dist
├── index.d.ts // types that will be picked up by typescript / javascript when importing our library
├── index.js // library compiled to commonjs
└── index.mjs // thin ecmascript wrapper on top of our library

Some remarks:

The index.js file is based on ./src/index.ts and allows us to have a very curated import experience for our users.

export * from './initializer'
export * from './minimal-live-connect'
export * from './standard-live-connect'

export * as emitter from './utils/emitter'
export * as eventBus from './events/bus'
export * as types from './utils/types'

The generated ./dist/index.mjs file is just a thin wrapper on top of commonjs modules and follows recommended best practices https://nodejs.org/api/packages.html#packages_dual_commonjs_es_module_packages

import cjs from './index.js';

export const LiveConnect = cjs.LiveConnect;
export const MinimalLiveConnect = cjs.MinimalLiveConnect;
export const StandardLiveConnect = cjs.StandardLiveConnect;
export const emitter = cjs.emitter;
export const error = cjs.error;
export const eventBus = cjs.eventBus;
export const fromError = cjs.fromError;
export const send = cjs.send;
export const types = cjs.types;

The changes to packages.json allow downstream dependencies to automatically pick the correct module for the module system they use:
https://nodejs.org/api/packages.html#conditional-exports

  "main": "./dist/index.js",
  "module": "./dist/index.mjs",
  "types": "./dist/index.d.ts",
  "exports": {
    ".": {
      "require": "./dist/index.js",
      "import": "./dist/index.mjs"
    },
    "./package.json": "./package.json"
  },

As a consequence of this we no longer need the ugly explicit import in liveconnectbuilder / prebid (i.e. import { LiveConnect } from 'live-connect-js/esm/initializer.js';). Instead we can use the nice import syntax we also use for other dependencies:
import { LiveConnect, MinimalLiveConnect } from 'live-connect-js';

Author Todo List:

• Add/adjust tests (if applicable)
• Build in CI passes
• Latest master revision is merged into the branch
• Self-Review
• Set Ready For Review status

[mschuwalow]

Replaced by files in package.json

[mschuwalow]

These were unused