Merge remote-tracking branch 'auscompgeek/push-username-highlight'

changelogs/client_server/newsfragments/2519.clarification

@@ -0,0 +1 @@
+Fix the ``.m.rule.contains_user_name`` default push rule to set the highlight tweak, matching Synapse and users' expectations.

specification/modules/push.rst

@@ -473,6 +473,9 @@ Definition (as a ``content`` rule):
             {
                 "set_tweak": "sound",
                 "value": "default"
+            },
+            {
+                "set_tweak": "highlight"
             }
         ]
     }