[Docs] Force using current protocol scheme for resources and links

If the docs is accessed with https, change all links to be https as well.

docs/_layouts/default.html

@@ -1,5 +1,15 @@
 <!DOCTYPE html>
 <html>
+  {% assign protocol_scheme = page.url | absolute_url | truncate: 5, "" %}
+  {%- capture site_url -%}
+    {%- if protocol_scheme == "https" -%}
+      <!-- This is a hack to force using HTTPS... -->
+      <!-- The URL of the docs should be changed in the repo settings instead -->
+      {{ site.github.url | replace: "http", "https" }}
+    {%- else -%}
+      {{ site.github.url }}
+    {%- endif -%}
+  {%- endcapture -%}
 
   {% include head.html %}