Announce Python 3.11 support (#43)

Author: jarrodmillman

pyproject.toml

@@ -1,5 +1,5 @@
 [build-system]
-requires = ["flit_core >=3.6,<4"]
+requires = ["flit_core >=3.7,<4"]
 build-backend = "flit_core.buildapi"
 
 [project]
@@ -16,6 +16,7 @@ classifiers = [
   "Programming Language :: Python :: 3.8",
   "Programming Language :: Python :: 3.9",
   "Programming Language :: Python :: 3.10",
+  "Programming Language :: Python :: 3.11",
 ]
 dynamic = ["description"]