CI on GitHub for GHC 8.0 - 9.10 (cabal) and 8.10 - 9.8 (stack)

[andreasabel]

This replaces the defunct Travis CI.

It does not test the cabal flag -f build-example for two reasons:

1. haskell-ci does not support cabal flags out of the box. The old .travis.yml was just manually updated to test both with the flag on and off.

2. cabal-test -f build-example fails on my system with "Sorry, this terminal doesn't support pretty ANSI codes". Might have been some change in ansi-terminal.

I also add a Stack CI for different snapshots that helps testing tasty-golden with different versions of its dependencies.

CI runs at: https://github.com/andreasabel/tasty-golden/pull/1