Standardize commit messages

During the team transition in 2021 January, we're attempting to document the general development practices that produced the existing artifacts in this repo. One thing we're not handling immediately is any sort of commit message standardization beyond "make it legible and take the usefulness of the content seriously".

This Issue is to revisit that, likely elaborating. @EncodePanda suggested this example https://chris.beams.io/posts/git-commit/ to start