matrix: Enable MSC4108 to allow Signing in with QR Code

modules/matrix/default.nix

@@ -124,6 +124,9 @@ in
         enable_room_list_search = true;
         encryption_enabled_by_default_for_room_type = "off";
         event_cache_size = "100K";
+        experimental = {
+          msc4108_enabled = true;
+        };
         federation_rr_transactions_per_room_per_second = 50;
         federation_client_minimum_tls_version = "1.2";
         forget_rooms_on_leave = true;