docs(): authentication tutorial with ionic and rxjs compact for angularfire2 ^rc.10 (angular#1721)

* authentication tutorial with ionic

authentication with ionic and firebase

* fix typo error

thank you @davideast for guiding me to present the article better

* small changes

* update rxjs-compat for angular v6

* update for angularfire rc 11

* no shortcode

Author: hiepxanh

docs/ionic/authentication.md

@@ -0,0 +1,101 @@
+# Step 1: install this plugin: 
+```
+ionic cordova plugin add cordova-universal-links-plugin
+ionic cordova plugin add cordova-plugin-buildinfo
+ionic cordova plugin add cordova-plugin-browsertab
+ionic cordova plugin add cordova-plugin-inappbrowser
+(for ios)
+ionic cordova plugin add cordova-plugin-customurlscheme 
+```
+
+# Step 2: Add Firebase to your Ionic
+
+ **Install firebase to angular project**
+
+Follow [this tutorial](https://github.com/angular/angularfire2/blob/master/docs/install-and-setup.md) to make a basic setup for your Ionic project.
+
+ **To set up in an Android app** 
+
+Go to [Firebase console](https://console.firebase.google.com/) then click **Add Firebase to your Android app** and follow the setup steps.
+
+
+# Step 3: Set up Firebase Authentication for Cordova ( summary from [firebase instruction](https://firebase.google.com/docs/auth/web/cordova))
+
+ **Setup Dynamic Link**
+ In the Firebase console, open the **Dynamic Links** section at bottom left panel, setup by their instruction
+
+ **Add dynamic link**
+ *Add this to config.xml at root level of project:*
+```xml
+     <universal-links>
+        <!-- this is dynamic link created in firebase -->
+        <host name="zm4e4.app.goo.gl" scheme="https" />
+        <!-- this is your firebase app link -->
+        <host name="routing-aadd4.firebaseapp.com" scheme="https">
+            <path url="/__/auth/callback" />
+        </host>
+    </universal-links>
+    <!-- for android -->
+    <preference name="AndroidLaunchMode" value="singleTask" />
+```
+
+  *Make sure your `<widget id="com.yourandroid.id" ... >` the same with android app's id you 
+  added in firebase*
+
+# Step 4: Add login code:
+at `login.service.ts` add this function: 
+```ts
+
+import { AngularFireAuth } from 'angularfire2/auth';
+import * as firebase from 'firebase/app';
+import AuthProvider = firebase.auth.AuthProvider;
+
+export class AuthService {
+    private user: firebase.User;
+	constructor(public afAuth: AngularFireAuth) {
+		afAuth.authState.subscribe(user => {
+			this.user = user;
+		});
+	}
+  
+  signInWithFacebook() {
+		console.log('Sign in with google');
+		return this.oauthSignIn(new firebase.auth.FacebookAuthProvider());
+	}
+
+  signInWithGoogle() {
+		console.log('Sign in with google');
+		return this.oauthSignIn(new firebase.auth.GoogleAuthProvider());
+	}
+
+  private oauthSignIn(provider: AuthProvider) {
+		if (!(<any>window).cordova) {
+			return this.afAuth.auth.signInWithPopup(provider);
+		} else {
+			return this.afAuth.auth.signInWithRedirect(provider)
+			.then(() => {
+				return this.afAuth.auth.getRedirectResult().then( result => {
+					// This gives you a Google Access Token.
+					// You can use it to access the Google API.
+					let token = result.credential.accessToken;
+					// The signed-in user info.
+					let user = result.user;
+					console.log(token, user);
+				}).catch(function(error) {
+					// Handle Errors here.
+					alert(error.message);
+				});
+			});
+		}
+	}
+}
+```
+
+# Common problems
+
+If you got error when build code like this:
+`UnhandledPromiseRejectionWarning: Unhandled promise rejection (rejection id: 1): TypeError: Cannot read property 'manifest' of undefined`
+
+Please, using this fix from [issue](https://github.com/nordnet/cordova-universal-links-plugin/issues/134):
+> Making this change in 'cordova-universal-links-plugin/hooks/lib/android/manifestWriter.js' fixed this issue for me:
+> [b2c5784#diff-d5955d9f4d88b42e5efd7a3385be79e9](https://github.com/nordnet/cordova-universal-links-plugin/commit/b2c5784764225319648e26aa5d3f42ede6d1b289#diff-d5955d9f4d88b42e5efd7a3385be79e9)

docs/ionic/v3.md

@@ -168,6 +168,10 @@ _This should add angularfire2, promise-polyfill and firebase entry in your proje
 "promise-polyfill": "^6.0.2",
 ```
 
+As the Angularfire2 v5+ rc10 requires rxjs6, you need to install rxjs-compat for angular version < 6.0:
+```
+npm install rxjs@6 rxjs-compat@6 promise-polyfill --save
+```
 ### Setup @NgModule
 
 Open your project in your favourite editor and open the `app.module.ts` file, under `src/app`