Merge pull request #438 from anoadragon453/anoa/group_id_example

Provide an example of the community ID format in the example config

mautrix_telegram/example-config.yaml

@@ -62,6 +62,8 @@ appservice:
 
     # Community ID for bridged users (changes registration file) and rooms.
     # Must be created manually.
+    #
+    # Example: "+telegram:example.com". Set to false to disable.
     community_id: false
 
     # Authentication tokens for AS <-> HS communication. Autogenerated; do not modify.