Add push rule for `m.room.server_acl` (#1190)

* Add push rule for `m.room.server_acl`

... per MSC3786.

* Update changelogs/client_server/newsfragments/1190.feature

Co-authored-by: Travis Ralston <travisr@matrix.org>

changelogs/client_server/newsfragments/1190.feature

@@ -0,0 +1 @@
+Add a `.m.rule.room.server_acl` push rule to match `m.room.server_acl` events, as per [MSC3786](https://github.com/matrix-org/matrix-spec-proposals/pull/3786).

content/client-server-api/modules/push.md

@@ -520,6 +520,33 @@ Definition:
 }
 ```
 
+**`.m.rule.room.server_acl`**
+
+Suppresses notifications for [`m.room.server_acl`](#mroomserver_acl) events.
+
+Definition:
+
+```json
+{
+    "rule_id": ".m.rule.room.server_acl",
+    "default": true,
+    "enabled": true,
+    "conditions": [
+        {
+            "kind": "event_match",
+            "key": "type",
+            "pattern": "m.room.server_acl"
+        },
+        {
+            "kind": "event_match",
+            "key": "state_key",
+            "pattern": ""
+        }
+    ],
+    "actions": []
+}
+```
+
 **`.m.rule.roomnotif`**
 
 Matches any message whose content is unencrypted and contains the text