Config: Move config mocks in own folder

To clean up the config folder, all mocks are now in it's own folder.

Signed-off-by: Philip Molares <philip.molares@udo.edu>

src/config/mock/app.config.mock.ts

@@ -0,0 +1,12 @@
+/*
+ * SPDX-FileCopyrightText: 2021 The HedgeDoc developers (see AUTHORS file)
+ *
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+import { registerAs } from '@nestjs/config';
+
+export default registerAs('appConfig', () => ({
+  port: 3000,
+  forbiddenNoteIds: ['forbiddenNoteId'],
+}));