doc: add an hidden toctree entry to ensure swh-*/index.rst are properly referenced

and thus prevent sphinx from complaining about rst files not being included in
a toctree without having to insert :orphan: everywhere.

docs/index.rst

@@ -116,3 +116,13 @@ Indices and tables
 * :ref:`modindex`
 * `URLs index <http-routingtable.html>`_
 * :ref:`search`
+
+
+.. ensure sphinx does not complain about index files not being included
+
+.. toctree::
+   :hidden:
+   :glob:
+
+   getting-started
+   swh-*/index