Examine source code of Chillify

{
  "manifest_version": 2,
  "name": "Chillify",
  "version": "1.0",
  "description": "Make your youtube chiller (by adding the chill guy everywhere).",
  "icons": {
    "48": "icon.png"
  },
  "permissions": [
    "activeTab",
    "tabs",
    "*://*.youtube.com/*"
  ],
  "content_scripts": [
    {
      "matches": [
        "*://*.youtube.com/*"
      ],
      "js": [
        "chill.js"
      ]
    }
  ],
  "browser_action": {
    "default_icon": "icon.png",
    "default_popup": "popup.html"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{330a8b2b-9fb6-4086-9349-b5422f9e00c2}"
    }
  }
}