Added GitHub Actions

[johnjasa]

Added two GH Actions scripts.
CI_every_commit runs on every push to WindSE and is where the Coveralls data is obtained.
CI_every_PR runs only on PR commits and contains longer tests, including the demos.

I've also added some PR and issue templates for GitHub

[jefalon]

Woah that was quick, Well done! What's the difference between these tests:

 CI_every_commit / Build (ubuntu-latest) (pull_request)
 CI_every_commit / Build (ubuntu-latest) (push)

[johnjasa]

Thanks! And great question. It's the same test so there's a bit of redundancy in this case. Why it's needed is that we want CI_every_commit to run for each push, but also for PRs. But if you have it set to only be run on pushes and not PRs, then I think there are situations where you can open a PR without triggering a push event. This introduces a double test that we can ignore, but is necessary for some edge case PRs.