Create pre-commit hook to run `rdm check`

If changes are made to the repository (e.g. changes to the remotes during repo migration) and subsequent changes are commited using git, then the links to the remotes in the Readme.md files stay outdated for quite a while. It would be good to have a pre-commit hook that runs `rdm check` on git commits to update remote urls (and possible other metadata we add later on).