Sending patches might be easier. Code is still available if you unzip plugin.

i'm not sure if many people use a github app

You do not need github app for that. You can use any git client you want.
Additionally, it is possible to do simple changes in-place.
Adds option of forking repo and sent pull requests.

By public repo, I don't necessarily mean github, you can use any other hosting you like.

i don't know, i haven't hosted any of my mods on github until now.
when i have implemented 2-3 more things the mod will be final anyway.
if you have a really cool idea what to mod next please tell me ;)