Add Changelog

Signed-off-by: Dave Rodgman <dave.rodgman@arm.com>
diff --git a/ChangeLog.d/ctr-perf.txt b/ChangeLog.d/ctr-perf.txt
new file mode 100644
index 0000000..bc04080
--- /dev/null
+++ b/ChangeLog.d/ctr-perf.txt
@@ -0,0 +1,3 @@
+Features
+   * Improve performance of AES-GCM, AES-CTR and CTR-DRBG when
+     hardware accelerated AES is not present (around 13-23% on 64-bit Arm).