add example of extending ansible_facts (#2040) (#2058)

* add example of extending ansible_facts

* Apply suggestions from code review

Co-authored-by: Felix Fontein <felix@fontein.de>

---------

Co-authored-by: Felix Fontein <felix@fontein.de>
(cherry picked from commit d693f43)

Co-authored-by: Sandra McCann <samccann@redhat.com>

docs/docsite/rst/dev_guide/developing_modules_general.rst

@@ -64,6 +64,13 @@ Info and facts modules, are just like any other Ansible Module, with a few minor
 5. They MUST NOT make any changes to the system.
 6. They MUST document the :ref:`return fields<return_block>` and :ref:`examples<examples_block>`.
 
+You can add your facts into ``ansible_facts`` field of the result as follows:
+
+.. code-block:: python
+
+    module.exit_json(changed=False, ansible_facts=dict(my_new_fact=value_of_fact))
+    
+
 The rest is just like creating a normal module.
 
 Verifying your module code