Composable Homepage (#6486)

feat: implement homepage plugin

plugins/home/dev/index.tsx

@@ -0,0 +1,27 @@
+/*
+ * Copyright 2021 The Backstage Authors
+ *
+ * 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 React from 'react';
+import { createDevApp } from '@backstage/dev-utils';
+import { homePlugin, HomepageCompositionRoot } from '../src/plugin';
+
+createDevApp()
+  .registerPlugin(homePlugin)
+  .addPage({
+    element: <HomepageCompositionRoot />,
+    title: 'Root Page',
+    path: '/',
+  })
+  .render();