Update github actions to use caching/not set up the environment every time

[kaijagahm]

Let's see if we can make the website build a little faster...

[jnywong]

This takes a bit of work, but you could pre-build a container image with all of your software requirements and pull that into the GHA:

• https://dev.to/mikerogers0/using-docker-to-speed-up-my-github-action-2333
• https://docs.github.com/en/actions/writing-workflows/choosing-where-your-workflow-runs/running-jobs-in-a-container

I would suggest publishing with a container registry such as quay.io or even GitHub's own container registry rather than DockerHub.