Note to disable URL Previews for grafana webhooks

chat/matrix/bridges.markdown

@@ -77,6 +77,9 @@ This API translates incoming webhooks into generic webhooks (hookshot). The sour
 1. Create a generic webhook using hookshot (see above)
 2. Use the `<hook>` URL part from hookshot with the base URLs listed below
 
+Optional (but recommended): Disable URL Previews (in Room > Settings). Otherwise URL Previews may generate error
+messages when previewing links sent by the webhook which require authentication.
+
 ### Grafana webhook notification
 
 Base URL: `https://webhooks.mbot.ethz.ch/webhook/grafana/<hook>`