fix(alipay): adjust pay function properties (#3197)

* fix bug 'Success is not a function #158'
terikon/cordova-plugin-photo-library#158

* alipay: add optional success, error callback
for pay()  method

src/@ionic-native/plugins/alipay/index.ts

@@ -15,7 +15,7 @@ import { Cordova, IonicNativePlugin, Plugin } from '@ionic-native/core';
  * constructor(private alipay: Alipay) {
  *
  * //alipayOrder is a string that has been generated and signed by the server side.
- * this.alipay.pay(alipayOrder)
+ * this.alipay.pay(alipayOrder, success, error)
  *    .then(result => {
  *       console.log(result); // Success
  *    })
@@ -44,7 +44,7 @@ export class Alipay extends IonicNativePlugin {
    * @returns {Promise<any>} Returns a Promise that resolves with the success return, or rejects with an error.
    */
   @Cordova()
-  pay(order: string): Promise<any> {
+  pay(order: string, success?: (res?: any) => void, error?: (err?: any) => void): Promise<any> {
     return;
   }
 }

src/@ionic-native/plugins/photo-library/index.ts

@@ -125,7 +125,7 @@ export class PhotoLibrary extends IonicNativePlugin {
   @Cordova({
     observable: true
   })
-  getLibrary(options?: GetLibraryOptions): Observable<LibraryItem[]> {
+  getLibrary(success?: (res?: any) => void, error?: (err?: any) => void, options?: GetLibraryOptions): Observable<LibraryItem[]> {
     return;
   }