Move from Travis CI to Github Actions for continuous integration

[miltondp]

Is your feature request related to a problem? Please describe.
No.

Describe the solution you'd like
Move Travis CI continuous integration in ukbREST to Github Actions.

Describe alternatives you've considered

Additional context
Here are a couple of files showing how Github Actions was implemented in a real project.

[miltondp]

This is a nice starting point: https://ben-heil.github.io/2020-08-24-conda-actions/

[hakyim]

@miltondp did you want to give this a try? At the moment, I don't have anybody who can work on this.

[miltondp]

Hi @hakyim. Yes, I will work on this but after October 12 :)