Add change log entry for adding psa_key_agreement() API

Signed-off-by: Waleed Elmelegy <waleed.elmelegy@arm.com>
diff --git a/ChangeLog.d/add-psa-key-agreement.txt b/ChangeLog.d/add-psa-key-agreement.txt
new file mode 100644
index 0000000..771e6e2
--- /dev/null
+++ b/ChangeLog.d/add-psa-key-agreement.txt
@@ -0,0 +1,3 @@
+Features
+   * Add a new psa_key_agreement() PSA API to perform key agreement and return
+     an identifier for the newly created key.