Update skipping documentation to include usage of allow_module_level kwarg

Author: georgeyk

doc/en/skipping.rst

@@ -54,6 +54,15 @@ by calling the ``pytest.skip(reason)`` function:
         if not valid_config():
             pytest.skip("unsupported configuration")
 
+It is also possible to skip the whole module using
+``pytest.skip(reason, allow_module_level=True)`` at the module level:
+
+
+.. code-block:: python
+
+    if not enabled_platform_edge_cases():
+        pytest.skip("unsupported platform", allow_module_level=True)
+
 The imperative method is useful when it is not possible to evaluate the skip condition
 during import time.