Add ref to docstring of Series:dtype (#24421)

Author: thoo

pandas/core/series.py

@@ -131,6 +131,7 @@ class Series(base.IndexOpsMixin, generic.NDFrame):
  dtype : str, numpy.dtype, or ExtensionDtype, optional
  dtype for the output Series. If not specified, this will be
  inferred from `data`.
+ See the :ref:`user guide <basics.dtypes>` for more usages.
  copy : bool, default False
  Copy input data.
  """