Add GitHub Actions CI workflow for CMake.

[nmoinvaz]

This PR adds GitHub Actions CI for CMake. It installs pre-requisite packages if needed, generates project files, and compiles them. Then it will run all the CMake tests.

AFAIK GitHub Actions shared runners support AVX2 so #138 may not be necessary.

[nmoinvaz]

You should be able to remove both AppVeyor and Travis CI. I can include that in this PR if you want.

[nmoinvaz]

Here is an example of what the GitHub Actions CI looks like:
https://github.com/nmoinvaz/c-blosc/actions/runs/87089046

[FrancescAlted]

Looks really good to me. I like the variety of scenarios that you are testing, specially SSE2/AVX2 deactivation and the possibility to link (or not) with external codecs. I think I am going to merge and deactivate TravisCI and AppVeyor promptly. Thank you!

[nmoinvaz]

Thanks! I will do one for c-blosc2 next.

[nmoinvaz]

For some reason AppVeyor is still showing up for the checks for this project.

https://ci.appveyor.com/project/FrancescAlted/c-blosc/builds/32449492

[FrancescAlted]

Good point. I deactivated the webhooks for AppVeyor and TravisCI. This should fix it.