Examine source code of Mono for YouTube

{
  "manifest_version": 3,
  "name": "Mono for YouTube",
  "version": "2.2.0",
  "description": "A distraction-free YouTube extension.",
  "browser_specific_settings": {
    "gecko": {
      "id": "{a6451854-795c-4f40-af7f-6238fb463108}"
    }
  },
  "content_scripts": [
    {
      "css": [
        "styles.css"
      ],
      "matches": [
        "https://www.youtube.com/*"
      ]
    }
  ],
  "icons": {
    "128": "art/icon_128.png"
  }
}