Add service worker support

README.md

@@ -146,7 +146,12 @@ A parent map that houses settings specific to creating progressive web applicati
 
 #### `pwa.manifest`: object
 
-Specifies information for a [web app manifest](https://developer.mozilla.org/en-US/docs/Web/Manifest). For example:
+Specifies information for a [web app manifest](https://developer.mozilla.org/en-US/docs/Web/Manifest). If provided, the following `<meta>` tags are injected into the application's `index.html`:
+
+- `mobile-web-app-capable="yes"`: indicates to Chrome on Android that the application can be added to the user's homescreen.
+- `apple-mobile-web-app-capable="yes"`: indicates to iOS devices that the application can be added to the user's homescreen.
+
+For example:
 
 ```
 {
@@ -161,6 +166,43 @@ Specifies information for a [web app manifest](https://developer.mozilla.org/en-
 }
 ```
 
+#### `pwa.serviceWorker`: object
+
+Generates a fully-functional service worker that is activated on startup, complete with precaching and custom route handling. Alternatively, you can create your own service worker file and `@dojo/cli-build-app` will ensure it is copied to the correct output directory. Under the hood, the `ServicerWorkerPlugin` from `@dojo/webpack-contrib` is used to generate the service worker, and [all of its options](https://github.com/dojo/webpack-contrib/#service-worker-plugin) are valid `pwa.serviceWorker` properties. Note that if `pwa.serviceWorker.cachePrefix` is not included, it defaults to the `name` property from the application's `package.json`.
+
+```js
+{
+	"build-app": {
+		"pwa": {
+			"serviceWorker": {
+				"cachePrefix": "my-app",
+
+				// exclude the "admin" bundle from caching
+				"excludeBundles": [ "admin" ],
+
+				"routes": [
+					// Use the cache-first strategy for loading images, adding them to the "my-app-images" cache.
+					// Only the first ten images should be cached, and for one week.
+					{
+						"urlPattern": ".*\\.(png|jpg|gif|svg)",
+						"strategy": "cacheFirst",
+						"cacheName": "my-app-images",
+						"expiration": { "maxEntries": 10, "maxAgeSeconds": 604800 }
+					},
+
+					// Use the cache-first strategy to cache up to 25 articles that expire after one day.
+					{
+						"urlPattern": "http://my-app-url.com/api/articles",
+						"strategy": "cacheFirst",
+						"expiration": { "maxEntries": 25, "maxAgeSeconds": 86400 }
+					}
+				]
+			}
+		}
+	}
+}
+```
+
 #### `build-time-render`: object
 
 Renders the application to HTML during the build and in-lines the critical CSS. This allows the application to effectively render static HTML pages and provide some advantages of SSR (server side rendering) such as performance, SEO etc without the complexities of running a server to support full SSR.