Include Calls (#720)

* Get Call module

* The call event

* Update onCall index.d.ts

src/structures/index.js

@@ -13,5 +13,6 @@ module.exports = {
     GroupNotification: require('./GroupNotification'),
     Label: require('./Label.js'),
     Order: require('./Order'),
-    Product: require('./Product')
+    Product: require('./Product'),
+    Call: require('./Call')
 };