docs(changelog): changelog for v2.13 release

Generated this change-log using below command:
npm run release -- --skip.commit --skip.tag --release-as 2.13.0

Change-Id: Ibb0623f04c641b65a03deaffd50a5a8b65637419
Signed-off-by: Govindraj Raja <govindraj.raja@arm.com>
diff --git a/package.json b/package.json
index 0908528..6061bf8 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "trusted-firmware-a",
-  "version": "2.12.0",
+  "version": "2.13.0",
   "license": "BSD-3-Clause",
   "type": "module",
   "private": true,