Examine source code of By Design m

{
  "manifest_version": 3,
  "version": "7.0.1",
  "name": "By Design m",
  "description": "removes thumbnails and plays videos in grayscale — so you watch only what matters, not what looks tempting",
  "homepage_url": "https://github.com/parth721/web-extention-c-",
  "default_locale": "en",
  "browser_specific_settings": {
    "gecko": {
      "id": "bydesign4u@yahoo.com",
      "strict_min_version": "125.0"
    }
  },
  "content_scripts": [
    {
      "matches": [
        "*://*.youtube.com/*"
      ],
      "js": [
        "common.js",
        "modify_an.js"
      ],
      "run_at": "document_start"
    }
  ],
  "options_ui": {
    "page": "options.html"
  },
  "permissions": [
    "storage",
    "activeTab"
  ],
  "action": {
    "default_icon": {
      "48": "icons/icon48.png"
    },
    "default_title": "ByDesign",
    "default_popup": "options.html"
  }
}