Examine source code of Switch Search Engine

{
  "manifest_version": 2,
  "name": "Switch Search Engine",
  "version": "1.0.1",
  "description": "Switch between search engines in one click. Supports custom engines.",
  "icons": {
    "16": "img/icon16.png",
    "32": "img/icon32.png",
    "48": "img/icon48.png",
    "128": "img/icon128.png"
  },
  "background": {
    "scripts": [
      "common.js",
      "background.js"
    ]
  },
  "content_scripts": [
    {
      "run_at": "document_end",
      "matches": [
        "*://*.startpage.com/*",
        "*://duckduckgo.com/*",
        "*://*.ecosia.org/*",
        "*://gibiru.com/*",
        "*://metager.org/*",
        "*://metager.de/*",
        "*://you.com/*",
        "*://www.onesearch.com/*",
        "*://*.bing.com/*",
        "*://search.brave.com/*",
        "*://yandex.ru/*",
        "*://yandex.com/*",
        "*://www.google.com/*",
        "*://search.yahoo.com/*",
        "*://search.yahoo.co.jp/*",
        "*://search.goo.ne.jp/*",
        "*://en.wikipedia.org/*"
      ],
      "js": [
        "common.js",
        "content.js"
      ]
    }
  ],
  "permissions": [
    "tabs",
    "storage"
  ],
  "web_accessible_resources": [
    "img/engines/*",
    "img/icon16.png",
    "img/icon32.png",
    "img/icon48.png",
    "img/icon128.png",
    "options.js"
  ],
  "commands": {
    "_execute_browser_action": {
      "suggested_key": {
        "default": "Ctrl+Alt+S"
      },
      "description": "Switch to next search engine"
    }
  },
  "options_ui": {
    "page": "options.html",
    "open_in_tab": true
  },
  "browser_action": {
    "default_icon": {
      "48": "img/icon48.png",
      "128": "img/icon128.png"
    },
    "default_title": "Switch Search Engine"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{23cd4523-1143-4efb-b849-b1c454172aa6}",
      "strict_min_version": "140.0",
      "data_collection_permissions": {
        "required": [
          "none"
        ],
        "optional": []
      }
    },
    "gecko_android": {
      "strict_min_version": "142.0"
    }
  }
}