Get rid of the UMD bundle: not pratical, not minimified so not ready for production, nor for reuse.
This lets remove the webpack build which was not used anymore.

• core build: everything is done with tsc and simplify pack
• remove webpack configuration
• Move typedoc in the package where it is used (make it easier to detect usage)
• remove unused dependencies:
  • better-docs (use typedoc instead)
  • webpack loaders (css, file, style, url)
  • babel
  • circular-dependency-plugin (webpack plugin)
  • webpack
  • cross-env
• core build: tsc only

BREAKING CHANGE: the UMD bundle is no more provided in the npm package

Notes

• The removing of webpack was made possible with chore: migrate to storybook v7 #230: we switched to Vite to power Storybook.
• See [build] Update the TypeScript configuration: enable isolatedModules #268 for a potential replacement of the circular-dependency-plugin webpack plugin removed as part of this PR
• I have checked the result of npm pack: the package sems OK. The ts-example build pass, so this confirms that the npm package seems correct.