Examine source code of Spell Checker for Emails

{
  "manifest_version": 2,
  "name": "Spell Checker for Emails",
  "version": "1.0",
  "description": "Kiểm tra chính tả trước khi gửi email.",
  "permissions": [
    "activeTab",
    "storage"
  ],
  "icons": {
    "48": "icons/icon.png"
  },
  "browser_action": {
    "default_popup": "popup.html",
    "default_title": "Spell Checker"
  },
  "content_scripts": [
    {
      "matches": [
        "https://mail.google.com/*",
        "https://outlook.live.com/*"
      ],
      "js": [
        "content.js"
      ]
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{72323ecd-b802-4a61-96b5-0f32e0ddedd1}"
    }
  }
}