Allow for python up to 3.10

Tested building and `pip install -e .` with 3.10, it works OK.
We should start prepping the migration to newer versions as well,
p3.11 already won't work.

Author: 5roop

setup.py

@@ -65,6 +65,8 @@
         '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',
     ],
 
     # What does your project relate to?