Add missing typing stub packages for mypy

[jayqi]

Fixes our failing build.

~Putting it in make lint seems like the most straightforward solution since it's only required for mypy checks. Running it multiple times doesn't seem to add any overheard.~

After reading through this very confusing thread, apparently this solution was recently implemented.

[github-actions[bot]]

🚀 Deployed on https://deploy-preview-72--zen-roentgen-1e5a72.netlify.app

[codecov[bot]]

Codecov Report

Merging #72 (5a9c9f1) into master (fccb7dd) will not change coverage. The diff coverage is n/a.

@@          Coverage Diff           @@
##           master     #72   +/-   ##
======================================
  Coverage    98.1%   98.1%           
======================================
  Files           8       8           
  Lines         382     382           
======================================
  Hits          375     375           
  Misses          7       7