add toctree to index file of the write_doc folder

Author: luisaFelixSalles

doc/source/getting_started/write_doc/index.rst

@@ -158,4 +158,10 @@ Documentation for the latest stable release of PyDPF-Core is hosted at
 In the upper right corner of the documentation's title bar, there is an option
 for switching from viewing the documentation for the latest stable release
 to viewing the documentation for the development version or previously
-released versions.
+released versions.
+
+.. toctree::
+    :maxdepth: 2
+    :hidden:
+
+    guide_lines_tutorials.rst