Improve documentation for github urls in the url parameter

Since gists are already supported using it's own gist url paramater, it might make sense to change the regular url paramater to demonstrate a regular github repo.

Just an idea, feel free to not implement it.

I'm mainly stuck on what I'm supposed to do to get this working: https://overpass-ultra.us/#query=url:https://github.com/thibaultmol/Random-shit/raw/refs/heads/main/Random%20overpass%20queries/Bicycle%20parkings%20near%20specific%20station