Examine source code of KeySwitch

{
  "manifest_version": 2,
  "name": "KeySwitch",
  "version": "1.3",
  "description": "Easily switch and map keys between different languages in your URLs.",
  "permissions": [
    "tabs",
    "activeTab",
    "<all_urls>",
    "storage"
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "browser_action": {
    "default_title": "KeySwitch",
    "default_icon": {
      "16": "icons/icon16.png",
      "32": "icons/icon32.png",
      "48": "icons/icon48.png",
      "128": "icons/icon128.png"
    }
  },
  "options_ui": {
    "page": "options.html",
    "browser_style": true
  },
  "commands": {
    "map-keys": {
      "suggested_key": {
        "default": "Ctrl+Shift+M"
      },
      "description": "Map URL keys to selected language"
    }
  },
  "applications": {
    "gecko": {
      "id": "KeySwitch@example.com"
    }
  }
}