DOC: reference the visualization page from the ecosystem one (#38731)

The link already exists in the other direction, so want to make sure
readers who come across the latter understand the built-in option.

Author: afeld

doc/source/ecosystem.rst

@@ -90,6 +90,9 @@ Compose is a machine learning tool for labeling data and prediction engineering.
 Visualization
 -------------
 
+While :ref:`pandas has built-in support for data visualization with matplotlib <visualization>`,
+there are a number of other pandas-compatible libraries.
+
 `Altair <https://altair-viz.github.io/>`__
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~