Examine source code of Vivaldfox

{
  "manifest_version": 2,
  "name": "Vivaldfox",
  "version": "1.4",
  "description": "Adds a Quick Command.",
  "icons": {
    "48": "icons/48.png",
    "96": "icons/96.png"
  },
  "permissions": [
    "tabs",
    "search",
    "bookmarks",
    "history"
  ],
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "contents/getKeyDown.js"
      ]
    }
  ],
  "applications": {
    "gecko": {
      "id": "vivaldfox@example.com"
    }
  },
  "background": {
    "scripts": [
      "main.js"
    ]
  },
  "browser_action": {
    "default_icon": {
      "48": "icons/48.png",
      "96": "icons/96.png"
    }
  }
}