Add release notes

[sleto-it]

This PR adds the release notes in the doc. This will help users better tracking releases and list of changes.
The content is taken from the valkey repo, 00-RELEASENOTES files (for the branches 8.0 and 7.2).

Links to the fixing PRs have been included (when the PR number was mentioned in the 00-RELEASENOTES).
Links to some GitHub Issues have been included as well (when the Issue number was mentioned in the 00-RELEASENOTES).

A ToC was included in the page to help navigation.

Release notes have been linked in the main Docs menu. Related PR in valkey-io.github.io: valkey-io/valkey-io.github.io#140.

Preview below

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[zuiderkwast]

This means we'll have to commit release notes to the doc repo every time we do a new release? It adds some extra work to the release process.

I would prefer that the website logic automatically would take the release notes from each release.

@stockholmux WDYT?

[stockholmux]

@zuiderkwast Yeah, I'd rather avoid committing the release notes to the docs repo for a variety of reasons.

Release notes are currently linked on every non-rc release from the releases page for each version, but admittedly that isn't quite obvious and misses anything put in RC releases.

GitHub Actions could be used to merge all this stuff together using minimal metadata on the website side (effectively adding a new element to array with each release). The website is quite good at including files inside the template, so we could do something like /release-notes/8.0.0, /release-notes/8.0.0-rc2, /release-notes/8.0.0-rc1 , etc. with a single version's release notes.

This is subtly different from what's being proposed, which is one giant page. (The giant page is also kind of an antipattern anyway).

[zuiderkwast]

@stockholmux I like this suggestion.

[stockholmux]

@sleto-it would you mind creating an issue on https://github.com/valkey-io/valkey-io.github.io so we can track getting this built? I'm glad to roll it into your PR valkey-io/valkey-io.github.io#140 as well.

[sleto-it]

Hi @stockholmux,
Sure, and thanks. Done: valkey-io/valkey-io.github.io#145