DOC: mention the PyPI license issue on the limitations page

Signed-off-by: Filipe Laíns <lains@riseup.net>

docs/reference/limitations.rst

@@ -38,6 +38,16 @@ tool will not work.
 We have work planned to fix this issue.
 
 
+License field on PyPI_
+======================
+
+``meson-python`` includes the license file in the metadata, instead of trying to
+match it to a classifier_ and omitting it, like some other backends do.
+Unfortunately, this results in the whole license text being shown on the
+*License* of PyPI_. You can read more about the issue and potential planned
+fixes in `#129`_.
+
+
 Platform-specific limitations
 =============================
 
@@ -59,5 +69,8 @@ question. Find how to do this in our
 
 
 .. _install_data: https://mesonbuild.com/Reference-manual_functions.html#install_data
+.. _PyPI: https://pypi.org/
+.. _classifier: https://pypi.org/classifiers/
+.. _#129: https://github.com/mesonbuild/meson-python/issues/129
 
 .. |install_data| replace:: ``install_data``