Examine source code of Grayscaler

{
  "manifest_version": 2,
  "name": "Grayscale",
  "version": "1.1",
  "description": "Applies a grayscale filter to selected websites.",
  "browser_action": {
    "default_popup": "popout/popout.html"
  },
  "icons": {
    "64": "icons/logo.png"
  },
  "content_scripts": [
    {
      "matches": [
        "*://*.youtube.com/*"
      ],
      "css": [
        "style.css"
      ],
      "js": [
        "script.js"
      ]
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{fbc17166-3b96-4afc-9927-e36ab7dd94b7}"
    }
  }
}