Automate GitHub Releases when new tags are pushed

[jacobtomlinson]

In dask/dask#11057 I added some GitHub Actions workflows to automatically create GitHub Releases when a new tag is pushed. Releases are just a page linked to a git tag with a title, some markdown text containing release notes and optional build artifacts for download.

We don't make use of the build artifact distribution in the Python community because we have PyPI and Conda Forge, but some users have expressed interest in having GitHub Releases as they show up in feeds, can be subscribed to, and generally make it easier to discover new releases in the GitHub ecosystem. See dask/dask#10956.

In this PR I've added the same GitHub Actions here which will automatically create a GitHub Release when a new tag is pushed. The release notes will be populated with the titles of all the PRs that went into the release, and have a link to the main Dask changelog at the bottom.

My goal here is to give value to the users who want Releases, but without adding any burden to the maintainer making the release. So this is pretty much set and forget once merged.

I've also created a Release for 2024.4.2 here manually because the Action needs at least one existing release as a frame of reference to calculate the changelog. We can manually clean this up after the next release.

[github-actions]

Unit Test Results

See test report for an extended history of previous test failures. This is useful for diagnosing flaky tests.

    29 files  ± 0      29 suites  ±0   11h 25m 4s ⏱️ - 5m 26s
 4 065 tests ± 0   3 952 ✅ + 2    109 💤 ±0  4 ❌  - 2 
55 026 runs  +18  52 611 ✅ +29  2 410 💤  - 8  5 ❌  - 3 

For more details on these failures, see this check.

Results for commit 9dd069a. ± Comparison against base commit 32de245.