Update custom.html

Add google analytics code

Author: Javier-Jimenez99

_includes/analytics-providers/custom.html

@@ -1,3 +1,12 @@
 <!-- start custom analytics snippet -->
+<!-- Google tag (gtag.js) -->
+<script async src="https://www.googletagmanager.com/gtag/js?id=G-1JFKS9BLJ2"></script>
+<script>
+  window.dataLayer = window.dataLayer || [];
+  function gtag(){dataLayer.push(arguments);}
+  gtag('js', new Date());
 
-<!-- end custom analytics snippet -->
+  gtag('config', 'G-1JFKS9BLJ2');
+</script>
+
+<!-- end custom analytics snippet -->