Examine source code of ChessSkins

{
  "manifest_version": 3,
  "name": "__MSG_appName__",
  "version": "2.1.0",
  "description": "__MSG_appDesc__",
  "default_locale": "en",
  "permissions": [
    "storage"
  ],
  "icons": {
    "16": "icons/icon16.png",
    "48": "icons/icon48.png",
    "128": "icons/icon128.png"
  },
  "action": {
    "default_popup": "popup.html",
    "default_icon": {
      "16": "icons/icon16.png",
      "48": "icons/icon48.png"
    },
    "default_title": "__MSG_appAction__"
  },
  "options_ui": {
    "page": "gallery.html",
    "open_in_tab": true
  },
  "content_scripts": [
    {
      "matches": [
        "*://lichess.org/*",
        "*://*.lichess.org/*",
        "*://lichess.com/*",
        "*://*.lichess.com/*",
        "*://www.chess.com/*",
        "*://chess.com/*"
      ],
      "js": [
        "content.js"
      ],
      "run_at": "document_start"
    }
  ],
  "web_accessible_resources": [
    {
      "resources": [
        "skins/*/skin.css",
        "boards/*/board.css"
      ],
      "matches": [
        "*://lichess.org/*",
        "*://*.lichess.org/*",
        "*://lichess.com/*",
        "*://*.lichess.com/*",
        "*://www.chess.com/*",
        "*://chess.com/*"
      ]
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "chessskins@nikags.github.io",
      "strict_min_version": "115.0",
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      }
    }
  }
}