enable sphinx.ext.napoleon (pydata#3180)

Author: DocOtak

doc/conf.py

@@ -66,6 +66,7 @@
     'sphinx.ext.intersphinx',
     'sphinx.ext.extlinks',
     'sphinx.ext.mathjax',
+    'sphinx.ext.napoleon',
     'numpydoc',
     'IPython.sphinxext.ipython_directive',
     'IPython.sphinxext.ipython_console_highlighting',
@@ -85,6 +86,9 @@
 autosummary_generate = True
 autodoc_typehints = 'none'
 
+napoleon_use_param = True
+napoleon_use_rtype = True   
+
 numpydoc_class_members_toctree = True
 numpydoc_show_class_members = False