feat(@schematics/angular): augment universal schematics to import platform-server shims

packages/schematics/angular/universal/files/src/__main@stripTsExtension__.ts.template

@@ -1,6 +1,15 @@
+/***************************************************************************************************
+ * Initialize the server environment - for example, adding DOM built-in types to the global scope.
+ *
+ * NOTE:
+ * This import must come before any imports (direct or transitive) that rely on DOM built-ins being
+ * available, such as `@angular/elements`.
+ */
+import '@angular/platform-server/init';
+
 <% if (hasLocalizePackage) { %>/***************************************************************************************************
  * Load `$localize` onto the global scope - used if i18n tags appear in Angular templates.
-*/
+ */
 import '@angular/localize/init';
 
 <% } %>import { enableProdMode } from '@angular/core';

packages/schematics/angular/universal/index_spec.ts

@@ -242,6 +242,14 @@ describe('Universal Schematic', () => {
     expect(tree.exists(filePath)).toEqual(true);
   });
 
+  it(`should add import to '@angular/platform-server/init' in main file`, async () => {
+    const tree = await schematicRunner.runSchematicAsync('universal', defaultOptions, appTree)
+      .toPromise();
+    const filePath = '/projects/bar/src/main.server.ts';
+    const contents = tree.readContent(filePath);
+    expect(contents).toContain('import \'@angular/platform-server/init\'');
+  });
+
   it(`should not add import to '@angular/localize' in main file when it's not a depedency`, async () => {
     const tree = await schematicRunner.runSchematicAsync('universal', defaultOptions, appTree)
       .toPromise();