Examine source code of Birtly

{
  "name": "Due.Work",
  "version": "0.0.3",
  "manifest_version": 2,
  "description": "To-do List, Tasks, Project Management and Team Communication Software",
  "icons": {
    "16": "images/icon-16x16.png",
    "32": "images/icon-32x32.png",
    "57": "images/icon-57x57.png",
    "72": "images/icon-72x72.png"
  },
  "default_locale": "en",
  "background": {
    "scripts": [
      "scripts/background.js"
    ]
  },
  "permissions": [
    "activeTab"
  ],
  "optional_permissions": [],
  "browser_action": {
    "default_icon": {
      "16": "images/icon-16x16.png",
      "32": "images/icon-32x32.png",
      "57": "images/icon-57x57.png",
      "72": "images/icon-72x72.png"
    },
    "default_title": "Due.Work",
    "default_popup": "popup.html"
  }
}