Added theme colour (#4811)

Most mobile browsers and now discord use this to set appropriate colours in their interface, in discords case it is setting the colour of the line on the side of the content preview of links

.themes/classic/source/_includes/head.html

@@ -15,6 +15,7 @@
   <meta name="HandheldFriendly" content="True">
   <meta name="MobileOptimized" content="320">
   <meta name="viewport" content="width=device-width, initial-scale=1">
+  <meta name="theme-color" content="#038FC7">
 
   {% capture canonical %}{{ site.url }}{% if site.permalink contains '.html' %}{{ page.url }}{% else %}{{ page.url | remove:'index.html' | strip_slash }}{% endif %}{% endcapture %}
   <link rel="canonical" href="{{ canonical }}">