Convert into a github action

[JustinPihony]

Pulling via checkout can mess with sbt dynver - making the script pull have to be before the code pull. It is more of an annoyance, but something to think about.

[sebastian-alfers]

What would change when converting this into a proper GH action?

[JustinPihony]

Mainly that the script(s) would be built in instead of having to check them out.