Service worker README update

README.md

@@ -7,7 +7,7 @@
 
 # pwa-lit-template
 
-> [Getting started](#getting-started) | [Build for production](#build-for-production) | [Create a new page](#create-a-new-page) | [Environment configuration](#environment-configuration) | [Browser support](#browser-support)
+> [Getting started](#getting-started) | [Build for production](#build-for-production) | [Create a new page](#create-a-new-page) | [Environment configuration](#environment-configuration) | [Service worker](#service-worker) | [Browser support](#browser-support)
 
 This project helps you to build Progressive Web Applications following the modern web standards, best practices and providing you with tools for that purpose. Out of the box, provides you with the following features:
 
@@ -166,6 +166,12 @@ render() {
 }
 ```
 
+### Service worker
+
+This project has configured the generation and injection of a service worker in the build process. But it is disabled by default. To enable it you just need to change the variable `GENERATE_SERVICE_WORKER` in the `rollup.config.js` to `true`.
+
+Also you can change the Workbox configuration too modifying the variable `workboxConfig` in that same file.
+
 ## Browser support
 
 - Chrome