Add caching to the CI

[stschaef]

Initially I had taken the CI for this repo from the CI in cubical-categorical-logic, but there were odd bugs where the workflow would not properly read from the cache

It is unclear if this also means there is a bug in cubical-categorical-logic's CI, or if I did something silly when porting over the workflow. Upon glancing at the action history there, it seems that I likely misconfigured something but I could not figure what after some debugging.

At this moment I am satisfied with an infrequently-run workflow that takes 15 minutes to run, but this workflow run could feasibly only take a couple of minutes if properly set up with caching

[stschaef]

maxsnew/cubical-categorical-logic#109