Examine source code of Minimalist Timer

{
  "manifest_version": 2,
  "name": "Minimalist Timer",
  "version": "1.0",
  "description": "A simple timer within your browser to track your tasks.",
  "browser_action": {
    "default_icon": "icons/timer-48.png",
    "default_popup": "popup.html",
    "default_title": "Timer"
  },
  "icons": {
    "48": "icons/timer-48.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{59efc104-1753-4893-a6e2-80333a16576f}"
    }
  }
}