fix(plugins): fix rxjs 6 build errors

#2439

src/@ionic-native/plugins/device-orientation/index.ts

@@ -1,9 +1,8 @@
 import { Injectable } from '@angular/core';
 import { Cordova, IonicNativePlugin, Plugin } from '@ionic-native/core';
-import { Observable } from 'rxjs/Observable';
+import { Observable } from 'rxjs';
 
 export interface DeviceOrientationCompassHeading {
-
   /**
    * The heading in degrees from 0-359.99 at a single moment in time. (Number)
    */
@@ -23,11 +22,9 @@ export interface DeviceOrientationCompassHeading {
    * The time at which this heading was determined. (DOMTimeStamp)
    */
   timestamp: number;
-
 }
 
 export interface DeviceOrientationCompassOptions {
-
   /**
    * How often to retrieve the compass heading in milliseconds. (Number) (Default: 100)
    */
@@ -37,7 +34,6 @@ export interface DeviceOrientationCompassOptions {
    * The change in degrees required to initiate a watchHeading success callback. When this value is set, frequency is ignored. (Number)
    */
   filter?: number;
-
 }
 
 /**
@@ -77,11 +73,21 @@ export interface DeviceOrientationCompassOptions {
   plugin: 'cordova-plugin-device-orientation',
   pluginRef: 'navigator.compass',
   repo: 'https://github.com/apache/cordova-plugin-device-orientation',
-  platforms: ['Amazon Fire OS', 'Android', 'BlackBerry 10', 'Browser', 'Firefox OS', 'iOS', 'Tizen', 'Ubuntu', 'Windows', 'Windows Phone']
+  platforms: [
+    'Amazon Fire OS',
+    'Android',
+    'BlackBerry 10',
+    'Browser',
+    'Firefox OS',
+    'iOS',
+    'Tizen',
+    'Ubuntu',
+    'Windows',
+    'Windows Phone'
+  ]
 })
 @Injectable()
 export class DeviceOrientation extends IonicNativePlugin {
-
   /**
    * Get the current compass heading.
    * @returns {Promise<DeviceOrientationCompassHeading>}
@@ -103,8 +109,9 @@ export class DeviceOrientation extends IonicNativePlugin {
     observable: true,
     clearFunction: 'clearWatch'
   })
-  watchHeading(options?: DeviceOrientationCompassOptions): Observable<DeviceOrientationCompassHeading> {
+  watchHeading(
+    options?: DeviceOrientationCompassOptions
+  ): Observable<DeviceOrientationCompassHeading> {
     return;
   }
-
 }