CI.md

This is a summary of the Python versions and platforms covered by the different CI platforms:

	3.7	3.8	3.9	3.10
Linux	AppVeyor¹ / Travis CI	Azure Pipelines / GitLab	CircleCI	GitHub Actions, Cirrus CI
macOS	AppVeyor¹ / Travis CI	Azure Pipelines	CircleCI	GitHub Actions, Cirrus CI
Windows	AppVeyor¹ / Travis CI	Azure Pipelines		GitHub Actions, Cirrus CI

¹ AppVeyor only runs the "basic" test to reduce load.

Non-x86 architectures are covered on Travis CI using Python 3.7.