release 21.7.0

Author: gaborbernat

docs/changelog.rst

@@ -6,6 +6,16 @@
 
 .. towncrier release notes start
 
+**********************
+ v21.7.0 (2026-07-21)
+**********************
+
+Features - 21.7.0
+=================
+
+- Declare support for Python 3.15: CI now tests against the CPython 3.15 beta, including the free-threaded ``3.15t``
+  build, and the ``Programming Language :: Python :: 3.15`` classifier is advertised. (:issue:`3192`)
+
 **********************
  v21.6.1 (2026-07-10)
 **********************