Add build using GitHub actions

[koppor]

This PR adds a GitHub workflow to enable checks from all JDKs from version 8 to 15.

The output of GitHub actions is better integrated in GitHub. Furthermore, the errors are highlighted better:

[THausherr]

Does this mean that each commit will trigger 8 builds, besides the Jenkins builds and the github travis builds? And same for everybody who has forked the project?

[msahyoun]

See https://infra.apache.org/github-actions-secrets.html

[THausherr]

"The ASF maxes out its runner allocation quite often, so a project needs to plan carefully to make best use of them for everyone's sake."

So to me this looks as if "no, won't do" is the answer for now.

[lehmi]

IMHO it doesn't make that much sense as we don't use github as primary repository, but as readonly mirror. So that those github actions are just another tool to verify our builds after a checkin. As Tilmans pointer shows the number of ASF runners are limited so that we shouldn't allocate them at all for a redundant process.

[koppor]

OK, got it. I just wanted to make an offer to replace Travis CI. I see ASF having the same limitations as Eclipse Foundation, which I just forgot. Sorry for the noise.