Examine source code of Twitter Setting Saver

{
  "version": "1.0.1",
  "name": "__MSG_extName__",
  "description": "__MSG_extDescription__",
  "default_locale": "en",
  "content_scripts": [
    {
      "js": [
        "content.js"
      ],
      "matches": [
        "https://twitter.com/home"
      ]
    }
  ],
  "icons": {
    "16": "icon_16.png",
    "48": "icon_48.png",
    "128": "icon_128.png"
  },
  "manifest_version": 2
}