[RCU] Problem adding a plugin

Hi,

I've tried to add a plugin to https://plugins.roundcube.net/packages/submit but without much luck: when I paste the repo:

https://github.com/gjedeer/roundcube-postfix-virtual-user-mapping.git

I'm getting: No valid/supported repository was found at the given URL

The error makes it sound like it's a problem with the submission process that you guys need to fix. Or, if it's a problem with my repo, maybe you have some suggestions what's wrong.

By the way, I tried to register on a forum to get support for this, but:

The user gdr with Email [....] (IP [......].21) is a Spam, please contact forum administrator.

Catch 22, because forum admin's email is not published...