add notice to plugins.ts

packages/app/src/plugins.ts

@@ -1,4 +1,19 @@
-/* eslint-disable notice/notice */
+/*
+ * Copyright 2020 Spotify AB
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
 import { default as HomePagePlugin } from '@backstage/plugin-home-page';
 import { default as WelcomePlugin } from '@backstage/plugin-welcome';
 export { HomePagePlugin, WelcomePlugin };