Examine source code of Icon Clock

{
  "manifest_version": 2,
  "name": "Icon Clock",
  "description": "Yet another toolbar icon clock",
  "version": "8",
  "browser_action": {},
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "homepage_url": "https://github.com/glitchub/icon_clock",
  "options_ui": {
    "page": "options.html"
  },
  "permissions": [
    "storage"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{8e272d2c-f463-4898-a8d4-4aa8afe7e889}"
    }
  }
}