A proxy for GitHub -> Discord webhooks, which automatically discards events from private repositories.
If you want to add an webhook to github you just prepend https://webhook.gruppe-adler.de/github?url= to the webhook url.
So if your Discord webhook URL is https://discordapp.com/api/webhooks/01/02/github you have to add an GitHub webhook with the following url: https://webhook.gruppe-adler.de/github?url=https://discordapp.com/api/webhooks/01/02/github.