DOC: Adding guide for the pandas documentation sprint (#19704)

Author: datapythonista

doc/source/contributing.rst

@@ -293,12 +293,9 @@ Some other important things to know about the docs:
   overviews per topic together with some other information (what's new,
   installation, etc).
 
-- The docstrings follow the **Numpy Docstring Standard**, which is used widely
-  in the Scientific Python community. This standard specifies the format of
-  the different sections of the docstring. See `this document
-  <https://github.com/numpy/numpy/blob/master/doc/HOWTO_DOCUMENT.rst.txt>`_
-  for a detailed explanation, or look at some of the existing functions to
-  extend it in a similar manner.
+- The docstrings follow a pandas convention, based on the **Numpy Docstring
+  Standard**. Follow the :ref:`pandas docstring guide <docstring>` for detailed
+  instructions on how to write a correct docstring.
 
 - The tutorials make heavy use of the `ipython directive
   <http://matplotlib.org/sampledoc/ipython_directive.html>`_ sphinx extension.