DOC: Pypi link

Author: MuellerSeb

docs/source/_templates/layout.html

@@ -6,4 +6,5 @@
     <a href="https://geostat-framework.org">GeoStat Website</a>
     <a href="https://github.com/GeoStat-Framework">GeoStat Github</a>
     <a href="https://geostat-framework.readthedocs.io">GeoStat ReadTheDocs</a>
+    <a href="https://pypi.org/user/geostatframework/">GeoStat PyPI</a>
   {% endblock %}