in footer, link to the most recent commit

[stevekrouse]

Could be neat to have this on every page so it's clear that you can submit pull requests.

We could also include the date of the most recent commit.

[stevekrouse]

Another note I made about this: embed github thing that says when the page was last updated, links to commit hash, and asks for contributions if you see typos

[stevekrouse]

Closed in favor of https://github.com/stevekrouse/unbreakable-links