Doc Link to accessors list in extending-xarray.rst (#6587)

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

Author: brynjarmorka

doc/internals/extending-xarray.rst

@@ -92,8 +92,8 @@ on ways to write new accessors and the philosophy behind the approach, see
 
 To help users keep things straight, please `let us know
 <https://github.com/pydata/xarray/issues>`_ if you plan to write a new accessor
-for an open source library. In the future, we will maintain a list of accessors
-and the libraries that implement them on this page.
+for an open source library. Existing open source accessors and the libraries
+that implement them are available in the list on the :ref:`ecosystem` page.
 
 To make documenting accessors with ``sphinx`` and ``sphinx.ext.autosummary``
 easier, you can use `sphinx-autosummary-accessors`_.