add room directory support

lib/models/requests/get_room_directory.dart

@@ -0,0 +1,28 @@
+import "package:freezed_annotation/freezed_annotation.dart";
+
+part "get_room_directory.freezed.dart";
+part "get_room_directory.g.dart";
+
+@Freezed(toJson: false, fromJson: false)
+@JsonSerializable(includeIfNull: false, explicitToJson: true)
+class const GetRoomDirectoryRequest({
+  final String? server,
+  final int limit = 48,
+  final String? since,
+  final PublicRoomsFilter? filter,
+}) with _$GetRoomDirectoryRequest {
+  Map<String, Object?> toJson() => _$GetRoomDirectoryRequestToJson(this);
+
+  factory GetRoomDirectoryRequest.fromJson(Map<String, Object?> json) =>
+      _$GetRoomDirectoryRequestFromJson(json);
+}
+
+@Freezed(toJson: false, fromJson: false)
+@JsonSerializable(includeIfNull: false)
+class const PublicRoomsFilter({final String? genericSearchTerm})
+    with _$PublicRoomsFilter {
+  Map<String, Object?> toJson() => _$PublicRoomsFilterToJson(this);
+
+  factory PublicRoomsFilter.fromJson(Map<String, Object?> json) =>
+      _$PublicRoomsFilterFromJson(json);
+}