✨ Add Google Tag Manager (#185)

apps/viewer/src/lib/google-tag-manager.ts

@@ -0,0 +1,23 @@
+export const gtmHeadSnippet = (
+  googleTagManagerId: string
+) => `<!-- Google Tag Manager -->
+(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','${googleTagManagerId}');
+<!-- End Google Tag Manager -->`
+
+export const gtmBodyElement = (googleTagManagerId: string) => {
+  if (document.getElementById('gtm-noscript')) return ''
+  const noScriptElement = document.createElement('noscript')
+  noScriptElement.id = 'gtm-noscript'
+  const iframeElement = document.createElement('iframe')
+  iframeElement.src = `https://www.googletagmanager.com/ns.html?id=${googleTagManagerId}`
+  iframeElement.height = '0'
+  iframeElement.width = '0'
+  iframeElement.style.display = 'none'
+  iframeElement.style.visibility = 'hidden'
+  noScriptElement.appendChild(iframeElement)
+  return noScriptElement
+}