support set metadata.recommend when create network-spec

[ianhe8x]

onf network-spec create -f

name: rococo-tick
displayName: Rococo Tick created by cli
protocol: polkadot-parachain
imageRepository: onfinality/rococo-collator
metadata:
  chainspec: tick
  # if start command is not defined as entrypoint, need to explicitly declare here
  command: rococo-collator
  recommend:
    nodeSpec: medium
    storageSize: 20
    imageVersion: rev-468d389
  imageVersion: rev-468d389

Allowing recommend field be be set in the new created network-spec.