Build and publish wheels for multiple platforms using pypa/cibuildwheel

[hardbyte]

As per the discussion in #165 this PR adds a Github Actions workflow to build and optionally publish binary artifacts for major operating systems and Python versions using cibuildwheel.

The action very much follows the example from the cibuildwheel docs - https://cibuildwheel.readthedocs.io/en/stable/setup/#github-actions

The publish step only runs when it sees a tagged commit - then this step will publish all the artifacts to pypi. To enable this you'll have to add a repository secret to your github repo. Pypi lets you create a tightly scoped api token that is allowed to upload packages for just one project - https://pypi.org/manage/account/token/

You'd add that as a repo secret - in this PR I've assumed a secret called PYPI_API_TOKEN - and this can be accessed by the github actions. Note this secret won't be accessible to a pull request from a fork (like mine), so the workflow would only run for pushes to your repository. I'd recommend having a read of github's security docs on this - https://docs.github.com/en/actions/security-guides/security-hardening-for-github-actions

An example of the output can be seen in my fork via this github action, and in the files automatically uploaded to this pypi release.

Replaces #87
Closes #165