DOC: Sidebar update

Author: MuellerSeb

docs/source/_templates/layout.html

@@ -3,6 +3,6 @@
     {{ super() }}
     <br />
     <a href="https://geostat-framework.org">GeoStat Website</a>
-    <br />
     <a href="https://github.com/GeoStat-Framework">GeoStat Github</a>
+    <a href="https://geostat-framework.readthedocs.io">GeoStat ReadTheDocs</a>
   {% endblock %}