Website should show reflog used in latest build

[coke]

There's no easy way to look at https://docs.raku.org/ and see which version of the git repository was used to build the version of the site we're looking at. We don't need to advertise it on every page, but something in the console, or hidden markup/comment, or an unlinked file displaying the git reflog of the last build would be great.

If something like this already exists, we should document it in the README.