Easily solve Docker image problems: VPN + domestic mirrors

First use domestic mirrors; if the domestic mirrors don't work, switch to VPN, alternating back and forth.

When using domestic mirrors, turn off the VPN; when using the VPN, remove the domestic mirrors (this is what I did; maybe it can work without doing that).

Clash default port is 7890

Domestic mirror sources:

   "registry-mirrors": [
    "https://mirror.ccs.tencentyun.com",
    "https://registry.docker-cn.com",
    "https://docker.mirrors.ustc.edu.cn",
    "https://hub-mirror.c.163.com"
  ]