Support always-latest links to versioned docs

[huonw]

Currently the docs for each version of Pants have a version in the URL, e.g. https://www.pantsbuild.org/2.21/docs/introduction/welcome-to-pants

In https://chat.pantsbuild.org/t/18888509/does-the-new-docsite-allow-latest-links-we-don-t-want-to-alw#17a3e060-95da-4879-a1e9-7254e042288b / https://pantsbuild.slack.com/archives/C0D7TNJHL/p1717762737437129 , there's discussion that this can be annoying in some circumstances, and it might be nice to support URLs that always point to the latest stable release, for instance, we're up to 2.21.0, so maybe one of these could be currently equivalent to the link above... and when we release 2.22 they'd automatically point to the new one:

• https://www.pantsbuild.org/docs/introduction/welcome-to-pants
• https://www.pantsbuild.org/latest/docs/introduction/welcome-to-pants
• https://www.pantsbuild.org/stable/docs/introduction/welcome-to-pants

NB. it'd be good to support a versioned permalink even for the latest docs (i.e. visiting the 2.21 link above should still work even now).

[lilatomic]

I'm generally in favour of a "latest" link. I imagine it has benefits for Search, where the link can just point to the current version.

[lilatomic]

Oh no I have so much power now, I can accidentally close issues when I hit the wrong shortcut D:
The linked thread talks to the downside to a "latest" link is that, when pages are renamed/consolidated, there's dead link. (To a lesser extent, this also happens with headings.) The thread mentions that we can configure redirects in the markdown, which I think is a good enough solution

[sureshjoshi]

I slightly prefer the "no-version" approach that Docusaurus uses, as it's marginally easier to read - but mostly because we also have docs on main and also the beta docs - so in that case, "latest" has mild ambiguity - in that it actually means "latest stable release".

But, a gust of wind could sway me to any of the other variants - as any implementation of this feature would make me happy!

[copart-jafloyd]

stable would be a better term than latest. I've seen docs where "latest" refers the devel version...

[cburroughs]

I'm gong to leave this opened for now as a marker for any followup and eventually supporting both (/stable and /the-version-num) urls like the Rust docs (if docusaurus makes that easier).