Added api for sending feedback

lib/api/mhsl/server/feedback/addFeedback.dart

@@ -0,0 +1,21 @@
+import 'dart:convert';
+
+import 'package:http/http.dart';
+import 'package:marianum_mobile/api/mhsl/mhslApi.dart';
+import 'package:http/http.dart' as http;
+
+import 'addFeedbackParams.dart';
+
+
+class AddFeedback extends MhslApi<void> {
+  AddFeedbackParams params;
+  AddFeedback(this.params) : super('server/feedback');
+
+  @override
+  void assemble(String raw) {}
+
+  @override
+  Future<Response>? request(Uri uri) {
+    return http.post(uri, body: jsonEncode(params.toJson()));
+  }
+}