add 3D touch plugin docs

src/plugins/3dtouch.ts

@@ -4,6 +4,7 @@ import {Observable} from 'rxjs/Observable';
  * @name 3DTouch
  * @description
  * @usage
+ * Please do refer to the original plugin's repo for detailed usage. The usage example here might not be sufficient.
  * ```
  * import {ThreeDeeTouch, ThreeDeeTouchQuickAction, ThreeDeeTouchForceTouch} from 'ionic-native';
  *
@@ -58,12 +59,14 @@ export class ThreeDeeTouch {
 
     /**
      * You need an iPhone 6S or some future tech to use the features of this plugin, so you can check at runtime if the user's device is supported.
+     * @returns {Promise<boolean>} returns a promise that resolves with a boolean that indicates whether the plugin is available or not
      */
     @Cordova()
     static isAvailable(): Promise<boolean> {return; }
 
     /**
      * You can get a notification when the user force touches the webview. The plugin defines a Force Touch when at least 75% of the maximum force is applied to the screen. Your app will receive the x and y coordinates, so you have to figure out which UI element was touched.
+     * @returns {Observable<ThreeDeeTouchForceTouch>} Returns an observable that sends a `ThreeDeeTouchForceTouch` object
      */
     @Cordova({
         observable: true
@@ -75,16 +78,26 @@ export class ThreeDeeTouch {
     })
     static configureQuickActions(quickActions: Array<ThreeDeeTouchQuickAction>): void {}
 
+    /**
+     * When a home icon is pressed, your app launches and this JS callback is invoked.
+     * @returns {Observable<any>} returns an observable that notifies you when he user presses on the home screen icon
+     */
     @Cordova({
         observable: true
     })
     static onHomeIconPressed(): Observable<any> {return; }
 
+    /**
+     * UIWebView and WKWebView (the webviews powering Cordova apps) don't allow the fancy new link preview feature of iOS9.
+     */
     @Cordova({
         sync: true
     })
     static enableLinkPreview(): void {}
 
+    /**
+     * Disabled the link preview feature, if enabled.
+     */
     @Cordova({
         sync: true
     })