Add workflow to build Python package as a wheel

[cpswan]

Is your feature request related to a problem? Please describe.

Installation instructions are presently quite complex, and should be reducible to 'install this wheel'

Describe the solution you'd like

A GitHub Actions workflow that builds the wheel for this package (using poetry build)

Describe alternatives you've considered

This should be on PyPi, but it's presently impossible to get an org account, and I'm loath to publish it using a personal account as it's not obvious how easy it will be to move things later.

Additional context

https://status.python.org/incidents/qy2t9mjjcc7g