Add changelog entry for #4357

Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
diff --git a/ChangeLog.d/psa_sign_message.txt b/ChangeLog.d/psa_sign_message.txt
new file mode 100644
index 0000000..2d77ec0
--- /dev/null
+++ b/ChangeLog.d/psa_sign_message.txt
@@ -0,0 +1,2 @@
+Features
+   * Implement psa_sign_message() and psa_verify_message().