fix: Constants export in index.js (#285)

* fix: add Constants export in index.js
* fix: add missing constants export in index.d.ts


Co-authored-by: Pedro S. Lopez <pedroslopez@me.com>

index.js

@@ -1,5 +1,7 @@
 'use strict';
 
+const Constants = require('./src/util/Constants');
+
 module.exports = {
     Client: require('./src/Client'),
     
@@ -15,5 +17,7 @@ module.exports = {
     PrivateContact: require('./src/structures/PrivateContact'),
     BusinessContact: require('./src/structures/BusinessContact'),
     ClientInfo: require('./src/structures/ClientInfo'),
-    Location: require('./src/structures/Location')
-};
+    Location: require('./src/structures/Location'),
+    
+    ...Constants
+};