将 Kubeconfig 中的证书文件路径转为证书数据

Kubeconfig中的certificate-authority、client-certificate和client-key都指的是某个具体文件路径，如何转化成数据格式的呢？

比如：

apiVersion: v1
kind: Config
clusters:
- cluster:
    certificate-authority: */ca.crt
    server: https://******
  name: demo
contexts:
- context:
    cluster: demo
    user: demo
  name: demo
current-context: demo
preferences: {}
users:
- name: demo
  user:
    client-certificate: */client.crt
    client-key: */client.key