Add workflow for running all Jupyter notebooks

[calebchiam]

We want to automate the running of all Jupyter notebooks on every change to ensure that notebooks run cleanly (and to serve as additional validation for the new changes).

Some resources on how to do this with GitHub Actions:

• https://github.com/mcullan/jupyter-actions
• https://innerjoin.bit.io/automate-jupyter-notebooks-on-github-9d988ecf96a6