Drop support for Drupal 9.x, 10.0 and 10.1

Created a patch. Moving to "Needs review" to prompt the community (and other maintainers) to review.

(Actually moving to needs review)

Determine if the Semantic Versioning spec says we should make a major version change, a minor version change, or a patch version change when we drop support for something outdated

I found https://github.com/semver/semver/issues/148 which suggests that I could even drop compatibility with older versions of Drupal core in a patch release (as long as I don't expose any part of Core's API or add any new features based on the newer versions).

Still researching this though.

I didn't hear any feedback in a few weeks, but experience with other modules suggests CI pipelines tend to work a bit better when you drop support in a new major version, so I created the 3.0.x branch and I've dropped D9 support in that branch. Should hopefully see a release soon, depending on my free time.

Automatically closed - issue fixed for 2 weeks with no activity.