Add Bing Verification meta-tag

Author: nau7ilus

_includes/domain_verification.html

@@ -0,0 +1,2 @@
+<!-- Bing Webmaster -->
+<meta name="msvalidate.01" content="DA40EAD7894F7D2A75863A6FE8D5F78E" />

_includes/head.html

@@ -47,6 +47,7 @@
   {% include gtm_head.html %}
   {% include google_analytics.html %}
   {% include cloudflare_analytics.html %}
+  {% include domain_verification.html %}
 
   {% if layout.common-ext-css %}
     {% for css in layout.common-ext-css %}