PEP 639: Mention implementations of this PEP in Hatch & Setuptools

pep-0639.rst

@@ -208,6 +208,15 @@ way to ensure that the full text of the license(s) are included with the
 package when distributed, as legally required, and allows other tools consuming
 the core metadata to unambiguously locate a distribution's license files.
 
+While dramatically simplifying and improving the present Python license
+metadata story, this specification standardizes and builds upon
+existing practice in the `Setuptools <setuptoolsfiles_>`__ and
+`Wheel <wheelfiles_>`__ projects.
+Furthermore, an up-to-date version of the current draft of this PEP is
+`already successfully implemented <hatchimplementation_>`__  in the popular
+PyPA `Hatch <hatch_>`__ packaging tool, and an earlier draft of the
+license files portion is `implemented in Setuptools <setuptoolspep639_>`__.
+
 Over time, encouraging the use of these fields and deprecating the ambiguous,
 duplicative and confusing legacy alternatives will help Python software
 publishers improve the clarity, accuracy and portability of their licensing
@@ -2751,6 +2760,8 @@ References
 .. _gnu: https://www.gnu.org/licenses/identify-licenses-clearly.html
 .. _guix: https://git.savannah.gnu.org/cgit/guix.git/tree/guix/licenses.scm?h=v1.3.0
 .. _guixlicense: https://guix.gnu.org/manual/en/html_node/package-Reference.html#index-license_002c-of-packages
+.. _hatch: https://hatch.pypa.io/latest/
+.. _hatchimplementation: https://discuss.python.org/t/12622/22
 .. _installedspec: https://packaging.python.org/specifications/recording-installed-packages/
 .. _interopissue: https://github.com/pypa/interoperability-peps/issues/46
 .. _licenseexplib: https://github.com/nexB/license-expression/