update docs; add python 3.11, 3.12 support

Author: shimizukawa

doc/index.rst

@@ -43,7 +43,7 @@ Support versions
 
 This product is tested with:
 
-* Python-3.8, 3.9, 3.10
+* Python-3.8, 3.9, 3.10, 3.11, 3.12
 * Django-3.2, 4.0, 4.2
 
 License