🪀 improve take-down docs a little

This adds a tangible list of informations required for copyright based take-down requests. It also tries to make some text passages easier to understand. Also I've changed the term 'verify' to 'check' to make it sound even more informal to make it more obvious that this wasn't written by a lawyer.

We've receive some copy right trolling on team@f-droid.org. With this update, it should be way more clear that trolls like these fail to come up with a plausible take-down request.