[plugins.json] Add cocoapods-cafswitcher

[Art Nichol]

Please add the following entry to the plugins.json file:

{
  "gem": "cocoapods-cafswitcher",
  "name": "CocoaPods Cafswitcher",
  "author": "handa",
  "url": "https://github.com/WendStation/cocoapods-cafswitcher.git",
  "description": "源码和二进制切换插件."
}

[Eric Amorde]

That URL is not publicly accessible - is this a private plugin?