Add ga tracking code

assets/js/app.js

@@ -105,7 +105,12 @@ window.stepper = {
             } else {
                 this.errors = {};
                 this.slideTo(null, this.step+1);
-                console.log('Anfrage versendet');
+
+                window.dataLayer = window.dataLayer || [];
+                function gtag(){dataLayer.push(window.arguments);}
+                gtag('js', new Date());
+
+                gtag('config', 'AW-394678894');
             }
         });
     },