Update README.md

Author: magefan

README.md

@@ -108,6 +108,7 @@ The code is licensed under [Open Software License ("OSL") v. 3.0](http://opensou
   * [Magento 2 Product Tabs Extension](https://magefan.com/magento-2/extensions/product-tabs)
   * [Magento 2 Extended Product Grid](https://magefan.com/magento-2-product-grid-inline-editor)
   * [Magento 2 Google Shopping Feed](https://magefan.com/magento-2-google-shopping-feed-extension)
+  * [Magento 2 Google Tag Manager](https://magefan.com/magento-2-google-tag-manager)
   * [Magento 2 Admin View Extension](https://magefan.com/magento-2-admin-view-extension)
   * [Magento 2 Zero Downtime Deployment](https://magefan.com/blog/magento-2-zero-downtime-deployment)
   * [Magento 2 Admin Email Notifications](https://magefan.com/magento-2-admin-email-notifications)