added link to advanced indexing guide in .loc docstring (#47520)

* added link to advanced indexing guide in .loc docstring

* changed refernce style for .loc docstring

Author: INDIG0N

pandas/core/indexing.py

@@ -521,6 +521,9 @@ def loc(self) -> _LocIndexer:
         sidewinder mark i          10      20
                    mark ii          1       4
         viper      mark ii          7       1
+
+        Please see the :ref:`user guide<advanced.advanced_hierarchical>`
+        for more details and explanations of advanced indexing.
         """
         return _LocIndexer("loc", self)