Examine source code of ChessExpert

{
  "name": "ChessExpert",
  "description": "The next-generation chess move calculator.",
  "version": "2.1.1",
  "manifest_version": 2,
  "browser_specific_settings": {
    "gecko": {
      "id": "support@chessexpert.io"
    }
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "permissions": [
    "tabs"
  ],
  "content_scripts": [
    {
      "matches": [
        "https://*.lichess.org/*",
        "https://*.chess.com/*",
        "https://*.chess24.com/*",
        "https://*.youtube.com/*",
        "https://*.kurnik.pl/*",
        "https://chessexpert.io/*"
      ],
      "js": [
        "content.js"
      ]
    }
  ],
  "browser_action": {
    "browser_style": true,
    "default_icon": "/images/32.png"
  },
  "icons": {
    "16": "/images/16.png",
    "32": "/images/32.png",
    "48": "/images/48.png",
    "128": "/images/128.png"
  }
}