ci: Add release pipeline to publish to PyPI

[fpgmaas]

PR Checklist

• [x] A description of the changes is added to the description of this PR.
• [x] If there is a related issue, make sure it is linked to this PR.
• [ ] If you've fixed a bug or added code that should be tested, add tests!
• [ ] If you've added or modified a feature, documentation in docs is updated

Description of changes

This adds a release pipeline so we can publish to PyPI. Publishing is triggered by creating a release on the repository. It alsoa dds some instructions to CONTRIBUTING.md with a proposed release workflow.

[SemyonSinchenko]

Is it possible to add any kind of tools (like release-please) to generate not only release, but also update CHANGELOG.md?

[fpgmaas]

Is it possible to add any kind of tools (like release-please) to generate not only release, but also update CHANGELOG.md?

That should be possible, but I have not worked with those tools yet. IMO it is good to separate that from this PR and solve the problem in steps; currently we can't release through the CI/Cd pipeline at all.