fix(background-mode): isEnabled and isActive return booleans

fixes #908

src/plugins/backgroundmode.ts

@@ -76,17 +76,21 @@ export class BackgroundMode {
 
   /**
   * Checks if background mode is enabled or not.
-  * @returns {Promise<boolean>} returns a promise that resolves with boolean that indicates if the background mode is enabled.
+  * @returns {boolean} returns a boolean that indicates if the background mode is enabled.
   */
-  @Cordova()
-  static isEnabled(): Promise<boolean> { return; }
+  @Cordova({
+    sync: true
+  })
+  static isEnabled(): boolean { return; }
 
   /**
   * Can be used to get the information if the background mode is active.
-  * @returns {Promise<boolean>} returns a promise that resolves with boolean that indicates if the background mode is active.
+  * @returns {boolean} returns a boolean that indicates if the background mode is active.
   */
-  @Cordova()
-  static isActive(): Promise<boolean> { return; }
+  @Cordova({
+    sync: true
+  })
+  static isActive(): boolean { return; }
 
   /**
   * Override the default title, ticker and text.