setup.py: Require setuptools >=58.5.0 (#1115)

.. so that "python3 setup.py sdist" ends up including these four
files in the resulting distribution source tarball:

- /third_party/yapf_third_party/yapf_diff/LICENSE
- /third_party/yapf_third_party/_ylib2to3/Grammar.txt
- /third_party/yapf_third_party/_ylib2to3/LICENSE
- /third_party/yapf_third_party/_ylib2to3/PatternGrammar.txt
diff --git a/setup.py b/setup.py
index ee5f620..605b78a 100644
--- a/setup.py
+++ b/setup.py
@@ -94,6 +94,9 @@
       },
       include_package_data=True,
       python_requires='>=3.7',
+      setup_requires=[
+          'setuptools>=58.5.0',  # for include_package_data fix (issue #1107)
+      ],
       install_requires=[
           'importlib-metadata>=6.6.0',
           'platformdirs>=3.5.1',