README tweaks

README.md

 channel defined in `http.listeners.grafana`. Note that this endpoint is currently
 unauthenticated.
 
-### GitHub Webhooks
+### GitHub Webhook
 ```json
 "github": {
 	"secret": "my_secret",
 sent to this channel unless overriden in `http.listeners.github.repositories`. Otherwise,
 unrecognised repositories will be ignored.
 
+GitHub can be configured to deliver webhooks to irccat on an organisation level which, combined
+with the `default_channel` setting, significantly reduces configuration effort compared to
+GitHub's old integrations system.
+
 ## IRC → Shell
 You can use irccat to execute commands from IRC: