docs(aio): Rename service worker files, update examples, move service worker under Techniques

aio/content/examples/service-worker-getting-started/src/app/prompt-update.service.ts

@@ -0,0 +1,20 @@
+import { Injectable } from '@angular/core';
+import { SwUpdate } from '@angular/service-worker';
+
+function promptUser(event): boolean {
+  return true;
+}
+
+// #docregion sw-activate
+@Injectable()
+export class PromptUpdateService {
+
+  constructor(updates: SwUpdate) {
+    updates.available.subscribe(event => {
+      if (promptUser(event)) {
+        updates.activateUpdate().then(() => document.location.reload());
+      }
+    });
+  }
+}
+// #enddocregion sw-activate