Archive versions below v0.69

[slorber]

React-Native versions <= 0.69 are "unmaintained": https://github.com/reactwg/react-native-releases#which-versions-are-currently-supported

If code is not backported for those unmaintained versions, why would we backport docs for them?

And most of those older versions do not even appear on the version dropdown:

So it makes sense to me to declutter the RN website and remove older versions, moving them to a standalone immutable netlify deployment https://reactnative-archive-august-2023.netlify.app/ (created under Meta Open Source team)

My proposal also add the archived versions to the /versions page so that those older docs remain accessible forever:

Preview Url: https://deploy-preview-3818--react-native.netlify.app/versions

Benefits: smaller website, faster prod deployment.
Drawback: it becomes harder to edit any archived version docs, but it's probably not a problem IMHO.

This PR also simplifies some code (see DocsVersionDropdownNavbarItem).

Note: this archiving feature is not part of Docusaurus, it's just plain React code and you are free to change the versionsArchived.json data structure if you want extra attributes.

My recommendation is to archive some versions regularly, maybe at least once every 6 months, to avoid an ever increasing list of "live versions" that do not bring any real value.

Important: use a real standalone Netlify/Vercel site for each archived site. The "permalinks" on Netlify now have an expiration date.

Note: before merging this PR, please approve it. I'll delete the appropriate /versioned_docs and /versioned_sidebars files before merging. I tried to keep this PR clean and easy to review.

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[Simek]

Thank you for working on this, and thinking about improving the archive process, LGTM! 👍

[slorber]

Thanks ;)

I wrote a RFC here with my proposals for a proper version archiving process that you could easily run on your own when needed: #3819

The goal of this PR is not to implement the perfect archiving system yet, but to be good enough to be merged as-is.

If someone at Meta can approve it fast, that would help me reduce the docs backport work needed in other PRs like this one: #3807

Once we all agree on a proper archiving process, it remains possible to rework this PR and migrate my current solution to the new cleaner one. The Netlify archive links in this PR could later be rewritten to become cleaner:

- "0.67": "https://reactnative-archive-august-2023.netlify.app/docs/0.67/getting-started",
+ "0.67": "https://archive.reactnative.dev/0.67/docs/getting-started",