docs(changelog): changelog for lts-v2.8.21 release

Change-Id: I5defda97abcdbe7ac0258fadea40dd51d09cb846
Signed-off-by: Release CI <ci@trustedfirmware.org>
diff --git a/readme.rst b/readme.rst
index cdb34a3..f522141 100644
--- a/readme.rst
+++ b/readme.rst
@@ -53,3 +53,4 @@
 
 
 
+