setup named releases for Technical Reference in RTD

[pdpinch]

As an open edX operator, I'd like a reliable source of information about toggles and settings that apply to the named release that I am deploying.

As the release notes writer, I'd like an easy way to be able to diff releases of the technical reference, so I can quickly build lists of new and removed settings for the release notes.

@pdpinch, Read The Docs allows setting multiple versions that are built. We could even add public versions for tagged releases. This way, users will be able to switch between them with the panel in the bottom right corner of the page. Example page, RTD config:

Originally posted by @Agrendalath in openedx/wg-build-test-release#133 (comment)

[NeOneSoft]

Hi @pdpinch!!!! May be this can be closed too If you are agree

[arbrandes]

Closing as stale.

[arbrandes]

Reopening, now in the docs repo where it might get the proper attention.