CI pipeline to run testsuite

[ketzacoatl]

It would be nice if PRs could show the status of the testsuite and not need to be built locally to determine if the PR breaks functionality.

[aaronhurt]

It's more than past time to update the GitHub actions used on this project. I should have the bandwidth to take a stab at that over the long weekend.

[ketzacoatl]

@aaronhurt is there a shortlist of updates you have in mind?

[ketzacoatl]

AFAICT, @tristanmorgan's recent updates have resolved this

https://github.com/fabiolb/fabio/pull/952/checks