[release]: generating website during prereleases can be improved

[kaicataldo]

The version of ESLint you are using.
master

The problem you want to solve.
There are currently a few issues with our site generation script surrounding the process of releasing prerelease versions.

1. The _data/rules.yml file in the website repo gets updated to include rules that have been added during the prerelease. This means that we end up with broken links on our rules page, because the actual documentation for these rules only exists in /docs/7.0.0/rules/.
2. We currently have to manually copy over the previous version of the documentation when we start a new major release cycle. It doesn't look like this was done with this current release cycle, so I believe the documentation in docs/6.0.0/ is the documentation that was generated during that prerelease cycle and would therefore be out of date.

Your take on the correct solution to problem.

1. Do not regenerate the _data/rules.yml file during prereleases (fixed by Chore: fix rules list for prereleases #13230).
2. I think this could be fixed by always copying over the current documentation into the corresponding /docs/{version}/ as well as the top level /docs/ directory, regardless of whether we're running a prerelease or not. The current system treats these directories as temporary pages (only up to date during the prerelease stage of our major release process), which I think is both confusing and forces us to manual update the files.

Are you willing to submit a pull request to implement this change?
Yes!

[eslint-deprecated]

Unfortunately, it looks like there wasn't enough interest from the team
or community to implement this change. While we wish we'd be able to
accommodate everyone's requests, we do need to prioritize. We've found
that issues failing to reach accepted status after 21 days tend to
never be accepted, and as such, we close those issues.
This doesn't mean the idea isn't interesting or useful, just that it's
not something the team can commit to.

Thanks for contributing to ESLint and we appreciate your understanding.

[kaicataldo]

Reopening this to track any work we do to solve #2.

[aladdin-add]

closing as outdated.