Examine source code of xiao-clock

{
  "manifest_version": 2,
  "name": "xiao-clock",
  "version": "0.6.0",
  "description": "A simple and small text based clock which sits in the toolbar. Ideal for fullscreen use of Firefox.",
  "permissions": [
    "menus"
  ],
  "icons": {
    "48": "icons/icon-48.png"
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "browser_action": {
    "default_title": "Xiao Clock"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{f5605424-3de5-4f59-bded-a0eee7968c04}"
    }
  }
}