add changelogs for 1.20.4
add changelogs for 1.20.4

kiranmeduri/amazon-ecs-agent,swipely/amazon-ecs-agent,kiranmeduri/amazon-ecs-agent,aws/amazon-ecs-agent,swipely/amazon-ecs-agent,aws/amazon-ecs-agent,kiranmeduri/amazon-ecs-agent,swipely/amazon-ecs-agent,kiranmeduri/amazon-ecs-agent,swipely/amazon-ecs-agent,aws/amazon-ecs-agent,aws/amazon-ecs-agent