Make it more obvious to use the Gitea backend for Forgejo/Codeberg

[mavit]

I tried to follow the instructions at https://anitya.readthedocs.io/en/latest/contributing.html#docker-podman but couldn't get it working, so these changes are untested.

[softwarefactory-project-zuul]

Build failed. More information on how to proceed and troubleshoot errors available at https://fedoraproject.org/wiki/Zuul-based-ci
https://fedora.softwarefactory-project.io/zuul/buildset/1332e985b45a46bcb267b0907e38cd22

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[Zlopez]

I tried to follow the instructions at https://anitya.readthedocs.io/en/latest/contributing.html#docker-podman but couldn't get it working, so these changes are untested.

What issue did you hit? Also you should be able to just run tox tests without the need to run the docker environment.

[Zlopez]

We can't rename backend as it will cause a mess in the database.

[Zlopez]

This is not a good idea, as it will invalidate the projects that are already have Gitea set as backend and they will not recognize the backend.

[mavit]

I'll look into doing something like the following instead:

<select id="backend" name="backend" required="" tabindex="3">
...
  <option value="Gitea">Gitea/Forgejo</option>
...
</select>

[Zlopez]

Doing that in HTML should be OK