Examine source code of Chess Trainer

{
  "manifest_version": 2,
  "name": "Chess Trainer",
  "description": "Enhances chess.com puzzles with an optional auto-flip 'defensive mode' and a configurable session timer with chimes. Inspired by chesspage1's course!",
  "version": "2.6",
  "icons": {
    "16": "icon-16.png",
    "48": "icon-48.png",
    "128": "icon-128.png"
  },
  "permissions": [
    "storage",
    "activeTab",
    "tabs",
    "https://www.chess.com/puzzles/learning"
  ],
  "web_accessible_resources": [
    "chime.mp3"
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "browser_action": {
    "default_title": "Defensive Mode",
    "default_popup": "popup.html"
  },
  "content_scripts": [
    {
      "matches": [
        "*://www.chess.com/puzzles/learning"
      ],
      "js": [
        "content-scripts/content.js"
      ]
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{6e1264bc-65b7-4d84-9b70-28b1368164ea}"
    }
  }
}