Add exec.sh script to execute command on app containers

exec.sh

@@ -0,0 +1,10 @@
+if [ $# -ne 2 ];
+  then echo "Expected 2 arguments: exec.sh env command"
+fi
+
+env=$1
+command=$2
+cluster="core-$env-app"
+
+taskId=$(aws ecs list-tasks --cluster $cluster --service-name "core-$env-app" --query "taskArns[0]" | grep -o "/$cluster/\w*" | sed "s@/$cluster/@@g")
+aws ecs execute-command --cluster "core-$env-app" --task $taskId --interactive --command "$command"