Add 3.10 and 3.11 to classifiers

I'm not updating .travis.yml since Travis CI is no longer
functioning.

setup.py

diff --git a/setup.py b/setup.py
index 2254d21..bbc2449 100644
--- a/setup.py
+++ b/setup.py
@@ -25,6 +25,8 @@
     'Programming Language :: Python :: 3.7',
     'Programming Language :: Python :: 3.8',
     'Programming Language :: Python :: 3.9',
+    'Programming Language :: Python :: 3.10',
+    'Programming Language :: Python :: 3.11',
     'Topic :: Software Development',
 ]