Added TypeScript definition for the update feature

Author: EddyVerbruggen

firebase.android.js

@@ -278,15 +278,15 @@ firebase.setValue = function (path, val) {
 };
 
 firebase.update = function (path, val) {
-    return new Promise(function (resolve, reject) {
-        try {
-            instance.child(path).updateChildren(firebase.toHashMap(val));
-            resolve();
-        } catch (ex) {
-            console.log("Error in firebase.update: " + ex);
-            reject(ex);
-        }
-    });
+  return new Promise(function (resolve, reject) {
+    try {
+      instance.child(path).updateChildren(firebase.toHashMap(val));
+      resolve();
+    } catch (ex) {
+      console.log("Error in firebase.update: " + ex);
+      reject(ex);
+    }
+  });
 };
 
 firebase.query = function (updateCallback, path, options) {

firebase.d.ts

@@ -116,6 +116,7 @@ declare module "nativescript-plugin-firebase" {
     export function resetPassword(options: ResetPasswordOptions): Promise<any>;
     export function push(path: string, value: any): Promise<PushResult>;
     export function setValue(path: string, value: any): Promise<any>;
+    export function update(path: string, value: any): Promise<any>;
     export function remove(path: string): Promise<any>;
     export function query(onValueEvent: (data: FBData) => void, path: string, options: QueryOptions): Promise<any>;
     export function addChildEventListener(onChildEvent: (data: FBData) => void, path: string): Promise<any>;