chore: update doc analytics.

docs/theme/partials/integrations/analytics.html

@@ -0,0 +1,7 @@
+<!-- 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-NMWC63S');</script>
+<!-- End Google Tag Manager -->

mkdocs.yml

@@ -28,6 +28,7 @@ theme:
 
 copyright: "Copyright © 2016-2019 Containous"
 
+# only to force the use of the analytics partials
 google_analytics:
   - 'UA-51880359-3'
   - 'docs.traefik.io'