Render externalDocs when it's available

src/main/template/main.handlebars

@@ -2,6 +2,11 @@
   {{#if info}}
   <div class="info_title">{{info.title}}</div>
   <div class="info_description markdown">{{{info.description}}}</div>
+  {{#if externalDocs}}
+  <h5>More documentations</h5>
+  <p>{{externalDocs.description}}</p>
+  <a href="{{externalDocs.url}}" target="_blank">{{externalDocs.url}}</a>
+  {{/if}}
   {{#if info.termsOfServiceUrl}}<div class="info_tos"><a href="{{info.termsOfServiceUrl}}">Terms of service</a></div>{{/if}}
   {{#if info.contact.name}}<div class='info_name'>Created by {{info.contact.name}}</div>{{/if}}
   {{#if info.contact.url}}<div class='info_url'>See more at <a href="{{info.contact.url}}">{{info.contact.url}}</a></div>{{/if}}