Add a missing changelog entry

Add a missing changelog entry for #3996: Allow loading external wrapped
keys.

Signed-off-by: Dave Rodgman <dave.rodgman@arm.com>
diff --git a/ChangeLog.d/external-wrapped-keys.txt b/ChangeLog.d/external-wrapped-keys.txt
new file mode 100644
index 0000000..ca29e0d
--- /dev/null
+++ b/ChangeLog.d/external-wrapped-keys.txt
@@ -0,0 +1,4 @@
+Bugfix
+   * Fixes a bug where, if the library was configured to include support for
+     both the old SE interface and the new PSA driver interface, external keys were
+     not loaded from storage. This was fixed by #3996.