DOC: Add reference to Text Extensions for Pandas project (pandas-dev#39783)

Author: frreiss

doc/source/ecosystem.rst

@@ -476,6 +476,14 @@ storing numeric arrays with units. These arrays can be stored inside pandas'
 Series and DataFrame. Operations between Series and DataFrame columns which
 use pint's extension array are then units aware.
 
+`Text Extensions for Pandas`_
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+``Text Extensions for Pandas <https://ibm.biz/text-extensions-for-pandas>``
+provides extension types to cover common data structures for representing natural language
+data, plus library integrations that convert the outputs of popular natural language
+processing libraries into Pandas DataFrames.
+
 .. _ecosystem.accessors:
 
 Accessors