Add docs PR preview

[mcbarton]

Description

Please include a summary of changes, motivation and context for this PR.

Fixes # (issue)

Inspired by the Jupyter Lite workflow here https://github.com/jupyterlite/jupyterlite/blob/main/.github/workflows/rtd-preview.yml this PR will attempt to make it so when someone puts in a PR it should try and build the docs and provide a preview to check things haven't broken

Type of change

Please tick all options which are relevant.

• Bug fix
• New feature
• Requires documentation updates

Testing

Please describe the test(s) that you added and ran to verify your changes.

Checklist

• I have read the contribution guide recently

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 76.15%. Comparing base (1c3f884) to head (f50e778).
Report is 114 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #379   +/-   ##
=======================================
  Coverage   76.15%   76.15%           
=======================================
  Files           8        8           
  Lines        3137     3137           
=======================================
  Hits         2389     2389           
  Misses        748      748