Examine source code of Time Machine (Google & YouTube)

{
  "manifest_version": 3,
  "name": "Time Machine (Search & Video Timeline)",
  "version": "1.1.0",
  "browser_specific_settings": {
    "gecko": {
      "id": "timemachine@retro-filter.local",
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      }
    }
  },
  "description": "Travels through the web's timeline. Filters modern or past search results on Google, YouTube, DuckDuckGo, and Bing, with Wayback Machine archive travel.",
  "permissions": [
    "storage",
    "activeTab"
  ],
  "host_permissions": [
    "*://*.google.com/*",
    "*://*.google.co.in/*",
    "*://*.google.co.uk/*",
    "*://*.google.ca/*",
    "*://*.google.de/*",
    "*://*.google.fr/*",
    "*://*.google.co.jp/*",
    "*://*.google.com.au/*",
    "*://*.google.it/*",
    "*://*.google.es/*",
    "*://*.google.com.br/*",
    "*://*.google.nl/*",
    "*://*.google.pl/*",
    "*://*.google.com.mx/*",
    "*://*.google.co.id/*",
    "*://*.google.com.pk/*",
    "*://*.google.com.ng/*",
    "*://*.google.ch/*",
    "*://*.google.be/*",
    "*://*.google.at/*",
    "*://*.google.se/*",
    "*://*.google.ru/*",
    "*://*.google.co.za/*",
    "*://*.google.com.tr/*",
    "*://*.google.com.tw/*",
    "*://*.google.com.hk/*",
    "*://*.google.com.sg/*",
    "*://*.youtube.com/*",
    "*://*.duckduckgo.com/*",
    "*://*.bing.com/*"
  ],
  "icons": {
    "48": "icon-48.png",
    "128": "icon-128.png"
  },
  "content_scripts": [
    {
      "matches": [
        "*://*.google.com/*",
        "*://*.google.co.in/*",
        "*://*.google.co.uk/*",
        "*://*.google.ca/*",
        "*://*.google.de/*",
        "*://*.google.fr/*",
        "*://*.google.co.jp/*",
        "*://*.google.com.au/*",
        "*://*.google.it/*",
        "*://*.google.es/*",
        "*://*.google.com.br/*",
        "*://*.google.nl/*",
        "*://*.google.pl/*",
        "*://*.google.com.mx/*",
        "*://*.google.co.id/*",
        "*://*.google.com.pk/*",
        "*://*.google.com.ng/*",
        "*://*.google.ch/*",
        "*://*.google.be/*",
        "*://*.google.at/*",
        "*://*.google.se/*",
        "*://*.google.ru/*",
        "*://*.google.co.za/*",
        "*://*.google.com.tr/*",
        "*://*.google.com.tw/*",
        "*://*.google.com.hk/*",
        "*://*.google.com.sg/*",
        "*://*.youtube.com/*",
        "*://*.duckduckgo.com/*",
        "*://*.bing.com/*"
      ],
      "js": [
        "content.js"
      ],
      "run_at": "document_idle"
    }
  ],
  "action": {
    "default_popup": "popup.html",
    "default_icon": "icon-48.png"
  }
}