Add changelog

Author: marc-gr

packages/aws/changelog.yml

@@ -1,4 +1,9 @@
 # newer versions go on top
+- version: "0.4.0"
+  changes:
+    - description: Add changes to use ECS 1.8 fields.
+      type: enhancement # can be one of: enhancement, bugfix, breaking-change
+      link: https://github.com/elastic/integrations/pull/721
 - version: "0.0.3"
   changes:
     - description: initial release