Update change log

Author: living180

docs/changes.rst

@@ -11,6 +11,9 @@ Change log
 * Fixed the cache panel to correctly count cache misses from the get_many()
   cache method.
 * Removed some obsolete compatibility code from the stack trace recording code.
+* Added a new mechanism for capturing stack traces which includes per-request
+  caching to reduce expensive file system operations.  Updated the cache and
+  SQL panels to record stack traces using this new mechanism.
 
 3.4.0 (2022-05-03)
 ------------------