ci: Publish from GitHub CI

[Gustl22]

Description

This allows publishing audioplayers from the GitHub CI.
The PR creation is available as a workflow dispatch (with option for prerelease) to not overwhelm the PR pipeline.

Checklist

• The title of my PR starts with a Conventional Commit prefix (fix:, feat:, refactor:,
  docs:, chore:, test:, ci: etc).
• I have read the Contributor Guide and followed the process outlined for submitting PRs.
• I have updated/added tests for ALL new/updated/fixed functionality.
• I have updated/added relevant documentation and added dartdoc comments with ///, where necessary.
• I have updated/added relevant examples in example.

Breaking Change

• Yes, this is a breaking change.
• No, this is not a breaking change.

Related Issues

[Gustl22]

Indirectly blocked by dart-lang/pub#4145, but we should do this in another PR anyway.
Or we use pubignore: https://stackoverflow.com/questions/69760021/what-should-be-ignored-in-darts-pubignore
Edit: This does not work, as that doesn't change the fact that these files are still checked in in git. So I removed them from git manually.

For test the workflow see: https://github.com/Gustl22/audioplayers/actions/runs/8032514104/job/21941993530
And with removing invalid files, passing: https://github.com/Gustl22/audioplayers/actions/runs/8037664053/job/21952740435

We could merge it, but for a release, we may need to do some changes / exclude the audio file with the non ascii char.

[spydon]

This won't work yet unfortunately, it's blocked by dart-lang/pub-dev#7177 which is solved in dart-lang/pub-dev#7462, but it seems like it will take a while to get that landed.

[Gustl22]

uh oh, thank you for the explanation! And thank you for investing time in such a useful feature. Gave my thumbs for issue and PR :D

[Gustl22]

This can be circumvented by adding exception --skip-validation. See dart-lang/pub#4145 (comment)