Allowing codeberg packages to be part of an universe

[defuneste]

Hello,

I am following @wlandau advice (r-multiverse/help#79 (reply in thread)) on updating part of the code from here before doing similar works on R-multiverse. The goal is to allow packages from codeberg to be referenced in a "universe" and specifically in R-multiverse.

• added a function lookup_codeberg_release that is checking for a codeberg release, using codeber API (more here https://codeberg.org/api/swagger#/repository/repoListReleases).

• included this function in get_release_version function

Those nearly empty packages offer good options for testing:

A simple package with one release: https://codeberg.org/r-codeberg/test.Rmultiverse.release
A package with no release: https://codeberg.org/defuneste/test.Rmultiverse
A package with a release and a pre-release: https://codeberg.org/defuneste/pot.pourri

I changed the obvious part but I may have missed some other parts and will try to update as needed.