[FEATURE] Google Tag Manager (#312)

* [FEATURE] Google Tag Manager

* [TASK] remove condition with regexp and use .if to improve performance

Configuration/TypoScript/Library/page.gtm.setupts

@@ -0,0 +1,24 @@
+# Google Analytics track pageview and add script for event tracking
+page.headerData.17895 = TEXT
+page.headerData.17895 {
+    if.isTrue = {$themes.configuration.tracking.ga_gtmid}
+    value (
+
+    <!-- Google Tag Manager -->
+    <script>
+        (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','{$themes.configuration.tracking.ga_gtmid}');
+    </script>
+    <!-- End Google Tag Manager -->
+)
+}
+
+page.3 = TEXT
+page.3 {
+    if.isTrue = {$themes.configuration.tracking.ga_gtmid}
+    value (
+
+    <!-- Google Tag Manager (noscript) -->
+    <noscript><iframe src="https://www.googletagmanager.com/ns.html?id={$themes.configuration.tracking.ga_gtmid}" height="0" width="0" style="display:none;visibility:hidden"></iframe></noscript>
+    <!-- End Google Tag Manager (noscript) -->
+)
+}

Configuration/TypoScript/Library/themes.googlewebmastertools.constantsts

@@ -12,3 +12,11 @@ themes.configuration.tracking.ga_account =
 # customsubcategory=googleWebMasterTools= Google Webmaster Tools
 # cat=theme,expert/googleWebMasterTools/; type=string; label= Google Search Console
 themes.configuration.tracking.ga_siteVerification =
+
+
+#############################################
+# Google Tag Manager
+#############################################
+# customsubcategory=googleWebMasterTools= Google Webmaster Tools
+# cat=theme,expert/googleWebMasterTools/; type=string; label= Google Tag Manager Id
+themes.configuration.tracking.ga_gtmid =