Examine source code of Pomodoro Improved

{
  "manifest_version": 2,
  "name": "Pomodoro Improved",
  "version": "2.4.0",
  "description": "实践番茄工作法: 工作时屏蔽浪费时间的网站, 休息时允许访问。A Firefox extension that helps you stay focused by blocking sites during work timers and letting you browse during break timers. ",
  "icons": {
    "16": "resources/icons/icon16.png",
    "48": "resources/icons/icon48.png",
    "128": "resources/icons/icon128.png"
  },
  "options_page": "options.html",
  "permissions": [
    "contextMenus",
    "notifications",
    "tabs",
    "<all_urls>"
  ],
  "browser_action": {
    "default_icon": "resources/icons/work_pending.png"
  },
  "web_accessible_resources": [
    "resources/icons/work_full.png",
    "resources/icons/break_full.png"
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "default_locale": "en",
  "browser_specific_settings": {
    "gecko": {
      "id": "{ae68043a-d123-4fde-86e9-06d2e8cc38f1}"
    }
  }
}