Show options for .m.rule.tombstone push rules

Part of vector-im/riot-web#8447

src/notifications/VectorPushRulesDefinitions.js

@@ -183,4 +183,15 @@ module.exports = {
             off: StandardActions.ACTION_DONT_NOTIFY,
         },
     }),
+
+    // Room upgrades (tombstones)
+    ".m.rule.tombstone": new VectorPushRuleDefinition({
+        kind: "override",
+        description: _td("When rooms are upgraded"), // passed through _t() translation in src/components/views/settings/Notifications.js
+        vectorStateToActions: { // The actions for each vector state, or null to disable the rule.
+            on: StandardActions.ACTION_NOTIFY,
+            loud: StandardActions.ACTION_HIGHLIGHT,
+            off: StandardActions.ACTION_DISABLED,
+        },
+    }),
 };