Haha, sorry Mopheus !
Contributing through github, especially small changes like this, is easier than you would think. You don't need to know anything about git or install stuff on your computer, it all happens in the browser. Just locate the file you want to edit (in this case RTL8812AU-01-add_new_cards.patch), click the edit button (pencil icon). Now edit the file (you're working in your private fork now, so don't worry about making mistakes), type a description and submit the proposed changes. In the next screen you can turn your edit into a pull request on the original project. Done!