add docformatter to contrib docs (#826)

* add docformatter to contrib docs

CONTRIBUTING.rst

@@ -119,12 +119,17 @@ Checkout the deepforest branch, update the `deepforest/meta.yaml` with the new v
    {% set sha256 = "fill new" %}
 
 
-
 Documentation
 -------------
 
 We are using `Sphinx <http://www.sphinx-doc.org/en/stable/>`_ and `Read the Docs <https://readthedocs.org/>`_ for the documentation.
 
+We use `Docformatter <https://pypi.org/project/docformatter/>`_ for formatting and style checking.
+
+.. code-block:: bash
+
+   $ docformatter --in-place --recursive deepforest/
+
 Update Documentation
 ^^^^^^^^^^^^^^^^^^^^
 
@@ -176,4 +181,4 @@ Start
 Note:
 Do not commit the build directory after making html.
 
-This version correctly follows reStructuredText (reST) conventions and includes code blocks, inline literals, and proper linking. Let me know if you need further adjustments!
+This version correctly follows reStructuredText (reST) conventions and includes code blocks, inline literals, and proper linking. Let me know if you need further adjustments!