Changelog entry for MBEDTLS_PSA_KEY_STORE_DYNAMIC

Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
diff --git a/ChangeLog.d/dynamic-keystore.txt b/ChangeLog.d/dynamic-keystore.txt
index d576dcd..c6aac3c 100644
--- a/ChangeLog.d/dynamic-keystore.txt
+++ b/ChangeLog.d/dynamic-keystore.txt
@@ -1,3 +1,9 @@
+Features
+   * When the new compilation option MBEDTLS_PSA_KEY_STORE_DYNAMIC is enabled,
+     the number of volatile PSA keys is virtually unlimited, at the expense
+     of increased code size. This option is off by default, but enabled in
+     the default mbedtls_config.h. Fixes #9216.
+
 Bugfix
    * Fix interference between PSA volatile keys and built-in keys
      when MBEDTLS_PSA_CRYPTO_BUILTIN_KEYS is enabled and