GitHub Actions CI

[Nicolasvb23]

Changes

Circle CI was replaced with the Github Actions CI with several ruby versions.
Updated Readme to reflect the Build status within the new CI

Objective

To leave explicit to all the community that the gem is actually supporting the newer Ruby versions, without the necessity to clone the repository locally and run the test suite 👍

[Nicolasvb23]

I can confirm that the CI is passing since I already triggered it in my forked repository.

[cainlevy]

This looks great, however I no longer have access to maintain this repository and I'm not clear who else might.

[Nicolasvb23]

Thanks for the response!

Lets wait until someone who is able to merge this to appear!

[cainlevy]

I do not have access to this repo, but I still have publishing rights on Rubygems. I've made a copy of the repo at https://github.com/cainlevy/scenic-mysql_adapter and included these commits.