Simplify release process

[mourner]

Closes #7718.

• Remove the outdated publish.sh.
• Add prepublishOnly a script that runs automatically on npm publish, making a clean dependencies install, running tests, generating the final builds and aborting if any of these steps fails.
• Update RELEASE.md, removing all unnecessary steps

A follow-up simplification would be to automate as much of the "docs" section as possible, eliminating manual steps like copying files, editing content manually etc., but I'll leave that to a different PR.

[Falke-Design]

I would suggest to use reference.html for the newest doc instead of redirecting to reference-1.7.1.html.
If a link of a method / option / etc. is shared it has always the same link and displays the newest version. Very useful for answers in issues or in documation of plugins. And yes this is currently already possible by using reference.html#marker but the most users don't know this and use the link of the specific version to share.

[mourner]

@Falke-Design good suggestion! Let's handle changes related to reference.html in a different PR though.