chore!: remove webpack build

[ehmicky]

This removes the Webpack build from this repository.

Reasons:

• This was added as an experimental feature but ended up creating many issues over time, despite being barely used.
• It is not even completely working.
• It makes migrating to pure ES modules (Use pure ES modules #495) more difficult.
• With the JavaScript system moving to pure ES modules and all the new bundling libraries which appeared in recent years, solutions relying on Webpack should not be needed anymore.
• It decreases the npm package size, which some users have complained about (Feature: Decrease bundle size by including only specified methods #154)

[kodiakhq]

This PR currently has a merge conflict. Please resolve this and then re-add the automerge label.