Examine source code of Locale Switcher

{
  "manifest_version": 2,
  "name": "Locale Switcher",
  "description": "Lets you quickly switch the browser locale to test localization on your website.",
  "version": "1.3.0",
  "icons": {
    "256": "icon/256.png"
  },
  "homepage_url": "https://github.com/locale-switcher/locale-switcher",
  "permissions": [
    "storage",
    "declarativeNetRequest",
    "activeTab",
    "scripting",
    "<all_urls>"
  ],
  "web_accessible_resources": [
    "override-language.js"
  ],
  "commands": {
    "_execute_action": {
      "suggested_key": {
        "default": "Ctrl+Shift+L"
      }
    }
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "browser_action": {
    "default_popup": "popup.html"
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "all_frames": true,
      "run_at": "document_start",
      "js": [
        "content-scripts/content.js"
      ]
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{ea6ccf94-00c4-4972-a28a-b9d3572b6131}"
    }
  }
}