Add pre commit bootstrap documentation

As exposed by https://gitlab.developers.cam.ac.uk/uis/devops/hr/utbs/utbs-webapp/-/merge_requests/46, it looks like we don't have documentation for a standard list of pre-commit hooks, so this MR adds one.

I'm obviously primarily coming to this as a consumer, so any input on whether these lists are correct would be appreciated (I've harvested it from @kh816's comment on https://gitlab.developers.cam.ac.uk/uis/devops/hr/utbs/utbs-webapp/-/merge_requests/46, this repo for Markdown and https://gitlab.developers.cam.ac.uk/uis/devops/experiments/api-boilerplate-prototype/-/blob/main/.pre-commit-config.yaml as a hopefully-representative Python project)