chore: added a call to action to contributors

Signed-off-by: Vitor Mattos <[email protected]>

Author: vitormattos

main/index.rst

@@ -7,4 +7,10 @@ Chose one of the sections below to access the corresponding documentation:
 
 - `User manual </user_manual/>`_
 - `Developer manual </developer_manual/>`_
-- `Admin manual </admin_manual/>`_
+- `Admin manual </admin_manual/>`_
+
+
+Reporting Documentation Bugs & How to Contribute
+=================================================
+
+If you find an error or omission in any of the manuals, we welcome your bug reports and contributions. Contribution to the documentation is very easy as the code is entirely `on GitHub and can be edited there online <https://github.com/LibreSign/documentation/>`_.