Examine source code of Engine Switcher

{
  "manifest_version": 2,
  "name": "Engine Switcher",
  "version": "0.9.0",
  "applications": {
    "gecko": {
      "id": "{44dc2f10-2812-48f1-bb39-e880679115b0}"
    }
  },
  "description": "Switch between various search engines in one click",
  "icons": {
    "256": "img/icon.png"
  },
  "page_action": {
    "browser_style": true,
    "default_icon": {
      "256": "img/icon.png"
    },
    "default_title": "Switch Engine!"
  },
  "background": {
    "scripts": [
      "dist/background.js"
    ]
  },
  "content_scripts": [
    {
      "run_at": "document_start",
      "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": [
        "dist/content.js"
      ],
      "css": [
        "dist/content_tippy.css"
      ]
    }
  ],
  "permissions": [
    "tabs",
    "storage"
  ],
  "web_accessible_resources": [
    "img/engines/*.svg",
    "img/engines/*.png",
    "img/engines/*.webp"
  ],
  "commands": {
    "_execute_page_action": {
      "suggested_key": {
        "default": "Ctrl+Alt+N",
        "linux": "Ctrl+Alt+N"
      },
      "description": "Switch to next search engine."
    }
  },
  "options_ui": {
    "page": "dist/options_ui.html",
    "open_in_tab": false
  }
}