Windows CI

Added in a job for running our tests on Windows using GitLab's shared runners (now accessible for free with the opening of the project). Only runs against 3.8 on a development merge at present due to these VMs being expensive to provision (takes about 10 minutes more than Linux) to avoid interrupting developer flow but this is up for debate

Successful run: https://gitlab.com/quantify-os/quantify-core/-/pipelines/205164647

Fixes #81 (closed)