Examine source code of YT Don't Recommend Button

{
  "manifest_version": 2,
  "name": "YouTube Don't Recommend Channel Button",
  "version": "2.0",
  "description": "Adds a custom button to YouTube video cards to block channels.",
  "permissions": [
    "activeTab",
    "https://www.youtube.com/*"
  ],
  "content_scripts": [
    {
      "matches": [
        "https://www.youtube.com/*"
      ],
      "js": [
        "content.js"
      ],
      "css": [
        "styles.css"
      ]
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{4ce42460-3f96-4e2c-a525-dda4a4afe8fb}"
    }
  }
}