Update nav_footer_custom.html

docs/_includes/nav_footer_custom.html

@@ -1,6 +1,6 @@
 <footer class="site-footer">
 <p>New Kingdoms is developed by Kujunda Seda OÜ and is dedicated to public domain.</p>
 <div style="height: 32px;">
-    <a href="https://github.com/kujunda-seda/new-kingdoms"><img src="assets/images/github-mark-white.svg" width="32px" /></a>
+    <a href="https://github.com/kujunda-seda/new-kingdoms"><img src="{{ site.baseurl }}/assets/images/github-mark-white.svg" width="32px" /></a>
 </div>
 </footer>