The Zen Cart plugins area now allows you to enter the Github repo for your contribution, if you are storing it in Github. Just enter

<your github username>/<your repo name>

in the Github Repository field. As an example, Better Together has "scottcwilson/zen_cart_better_together" in the Github Repository field.

You can see an example of the "Github Repository" button here:

https://www.zen-cart.com/downloads.php?do=file&id=126

If you want to add a Github repo to an existing contribution that you support, just send your humble moderator a PM. :)