Generate template files from kctrl package init

[liangyuanpeng]

Describe the problem/challenge you have

I want to generate a template carvel package from command of kctrl package init for quickly to know carvel package.

Describe the solution you'd like

Auto generate files (from https://github.com/carvel-dev/ytt/tree/develop/examples/playground/basics/example-demo) :

defaults.yml

#@data/values
---
echos:
- name: first
- name: second
  port: 8081
  text: "Hello #ytt World on 8081!"

demo.yml

#@ load("@ytt:data", "data")

#@ def labels():
app: echo
org: test
#@ end

#@ def name(echo):
#@   return "echo-"+echo.name
#@ end

kind: Pod
apiVersion: v1
metadata:
  name: echo-app
  labels: #@ labels()
spec:
  containers:
  #@ for/end echo in data.values.echos:
  - name: #@ name(echo)
    image: hashicorp/http-echo
    args:
    - #@ "-listen=:" + str(echo.port)
    - #@ "-text=" + echo.text

#@ if/end data.values.service.enabled:
---
kind: Service
apiVersion: v1
metadata:
  name: echo-service
spec:
  selector: #@ labels()
  ports:
  #@ for/end echo in data.values.echos:
  - name: #@ name(echo)
    port: #@ echo.port

schema.yml

#@data/values-schema
---
echos:
- name: ""
  port: 8080
  text: "Hello #ytt World on 8080!"
service:
  enabled: true

Anything else you would like to add:

---

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