Add 'view channel on Youtube' link

src/invidious/views/channel.ecr

@@ -31,6 +31,10 @@
 <% end %>
 </p>
 
+<p class="h-box">
+    <a href="https://www.youtube.com/channel/<%= ucid %>">View channel on YouTube</a>
+</p>
+
 <% videos.each_slice(4) do |slice| %>
 <div class="pure-g">
     <% slice.each do |video| %>