setup.py: Advertize support for python 3.11
diff --git a/setup.py b/setup.py
index b80d347..b2cc263 100755
--- a/setup.py
+++ b/setup.py
@@ -57,6 +57,7 @@
         "Programming Language :: Python :: 3.8",
         "Programming Language :: Python :: 3.9",
         "Programming Language :: Python :: 3.10",
+        "Programming Language :: Python :: 3.11",
         "Topic :: Software Development :: Build Tools",
     ],
     description="A collection of plugins for BuildStream.",