As TFA notes, either nothing gets done (you send-email and the other guy just doesn't see/want it) or something has to give, you have to create a github repository with the result of your patch or the other guy has to learn git-am.
Or you know he checks his email and takes the patch. When you use github you are using git. There is no way to commit from the github website, so if they have code on github then they must have interacted with git. Now that we have established they interact with git then they have the capability to interact with the patch feature if they so desire.
Actually, you can commit from github. Go to any file and hit Edit at the top right. It's a single file editor, so don't expect much out of it, but it is conceivable for someone to contribute without using git.
And to your point, you cannot add files via github.