docs: add AngularFire integration docs

Close #3931

Author: beeman

docs/documentation/stories/include-angularfire.md

@@ -0,0 +1,91 @@
+# Include AngularFire
+
+[Firebase](https://firebase.google.com/) is a mobile and web application platform with tools and infrastructure designed
+to help developers build high-quality apps. [AngularFire2](https://github.com/angular/angularfire2) is the official 
+Angular library to use Firebase in your apps.
+
+#### Create new project
+
+Create a new project and navigate into the project.
+
+```bash
+$ ng new my-app
+$ cd my-app
+```
+
+#### Install dependencies
+
+In the new project you need to install the required dependencies.
+
+```bash
+$ npm install --save angularfire2 firebase
+```
+
+#### Get Firebase configuration details
+
+In order to connect AngularFire to Firebase you need to get the configuration details.
+
+Firebase offers an easy way to get this, by showing a JavaScript object that you can copy and paste.
+
+- Log in to the [Firebase](https://firebase.google.com) console.
+- Create New Project or open an existing one.
+- Click `Add Firebase to your web app`.
+- From the modal window that pops up you copy the `config` object.
+
+```javascript
+  var config = {
+    apiKey: "your-api-key",
+    authDomain: "your-auth-domain",
+    databaseURL: "your-database-url",
+    storageBucket: "your-storage-bucket",
+    messagingSenderId: "your-message-sender-id"
+  };
+```
+
+#### Configure the Environment
+
+These configuration details need to be stored in our app, one way to do this using the `environment`. This allows you to 
+use different credentials in development and production.
+
+Open `src/environments/environment.ts` and add a key `firebase` to the exported constant:
+
+```typescript
+export const environment = {
+  production: false,
+  firebase: {
+    apiKey: 'your-api-key',
+    authDomain: 'your-auth-domain',
+    databaseURL: 'your-database-url',
+    storageBucket: 'your-storage-bucket',
+  }
+};
+```
+
+To define the keys for production you need to update `src/environments/environment.prod.ts`.
+
+#### Import and load FirebaseModule
+
+The final step is to import `AngularFireModule` and initialize it using the parameters from the `environment`.
+
+Open `src/app/app.module.ts` and add the following lines on the top of the file, with the other imports:
+
+```typescript
+import { AngularFireModule } from 'angularfire2';
+import { environment } from '../environments/environment';
+```
+
+To initialize AngularFire add the following line to the `imports` array inside the `NgModule`: 
+
+```typescript
+@NgModule({
+  // declarations
+  imports: [
+    // BrowserModule, etc
+    AngularFireModule.initializeApp(environment.firebase),
+  ]
+  // providers
+  // bootstrap
+})
+```
+
+#### Congratulations, you can now use Firebase in your Angular app!