3cloud-backend/docs/curl to add container to pod.md

PODID=7e0604d0-c228-4a8c-8bb7-27eaa8c96c1e

curl -X POST http://192.168.64.2:5000/api/workloads/containers
-H "Content-Type: application/json"
-d @- <<EOF { "pod": "${PODID}", "containers": [ { "docker_image": "joke_container", "container_name": "amazing-joke-server99", "ports": [ { "internal": 9092, "external": 8766, "use_dns": false } ], "env": { "PORT": "9092" } } ] } EOF