Github Actions + Containerize build process

[andrewabest]

At the moment Conventional is built on Appveyor.

We'd like to bring the build across to GHA as it will make it easier for contributors and consumers to work with.

At the same time, it would be good to containerize the build and its dependencies (i.e. SQL server) so that we can run a MacOS build as well, as Conventional has users on MacOS and they occasionally hit issues (like this one) that we are not testing for due to not having an Mac build.