Add tags to NodeBalancer creation API request schema

[zliang-akamai]

The API allows adding tags attribute during the creation.

curl -H "Content-Type: application/json" \
    -H "Authorization: Bearer $LINODE_TOKEN" \
    -X POST -d '{
      "region": "us-central",
      "tags": ["123", "234"]
    }' https://api.linode.com/v4/nodebalancers