test(language-service): test @angular/language-service can be loaded by tsserver.js (#14721)

integration/language_service_plugin/project/app/app.module.ts

@@ -0,0 +1,11 @@
+import { NgModule }      from '@angular/core';
+import { BrowserModule } from '@angular/platform-browser';
+
+import { AppComponent }  from './app.component';
+
+@NgModule({
+  imports:      [ BrowserModule ],
+  declarations: [ AppComponent ],
+  bootstrap:    [ AppComponent ]
+})
+export class AppModule { }