Autobuild fails on clean install

[AwesomestCode]

What's broken?
make autobuild is missing files.

Recreation steps:

1. Create a clean dev environment. This can easily be done by creating a new Codespace on GitHub.
2. Follow the README's instructions for building:
   a. python3 -m pip install -r source/requirements.txt
   b. make autobuild
3. Notice that the last command errors with the following output:

make: sphinx-autobuild: No such file or directory
make: *** [Makefile:36: autobuild] Error 127