Include GTM for site ser

public/typo3conf/ext/ep_theme/Configuration/TypoScript/Page/Main.typoscript

@@ -205,6 +205,21 @@ page {
     }
 }
 
+[site('identifier') == 'ser']
+    page.headerData.990 >
+    page.headerData.995 >
+    page.headerData.999 = TEXT
+    page.headerData.999.value (
+<!-- Google Tag Manager -->
+<script>(function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':
+new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],
+j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src=
+'https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);
+})(window,document,'script','dataLayer','GTM-MNKDKL9');</script>
+<!-- End Google Tag Manager -->
+    )
+[end]
+
 [page["backend_layout"] == 'pagets__popup']
     page.bodyTagCObject >
     page.bodyTagCObject = TEXT