Require Cython 0.29.28 and mark Py3.9/10 as supported.

Author: scoder

requirements.txt

@@ -1,2 +1,2 @@
-Cython>=0.29.24
+Cython>=0.29.28
 setuptools

setup.py

@@ -376,6 +376,8 @@ def write_file(filename, content):
         'Programming Language :: Python :: 3.6',
         'Programming Language :: Python :: 3.7',
         'Programming Language :: Python :: 3.8',
+        'Programming Language :: Python :: 3.9',
+        'Programming Language :: Python :: 3.10',
         'Programming Language :: Other Scripting Engines',
         'Operating System :: OS Independent',
         'Topic :: Software Development',