Examine source code of Sleeper League Importer

{
  "update_url": "https://clients2.google.com/service/update2/crx",
  "manifest_version": 3,
  "name": "Sleeper League Importer",
  "version": "0.5.3",
  "description": "Copy ESPN league history—including NFL.com leagues moved to ESPN—to Sleeper.",
  "minimum_chrome_version": "116",
  "permissions": [
    "activeTab",
    "declarativeNetRequest",
    "sidePanel",
    "storage",
    "tabs"
  ],
  "host_permissions": [
    "https://www.espn.com/*",
    "https://fan.api.espn.com/*",
    "https://fantasy.espn.com/*",
    "https://fantasy.nfl.com/*",
    "https://fantasyfootball.nfl.com/*",
    "https://lm-api-reads.fantasy.espn.com/*",
    "https://nextgenstats.nfl.com/*",
    "https://sleeper.com/*",
    "https://sleeper.app/*",
    "https://api.sleeper.app/*"
  ],
  "background": {
    "service_worker": "background.js",
    "type": "module"
  },
  "action": {
    "default_title": "Sleeper League Importer",
    "default_icon": {
      "16": "assets/icon16.png",
      "32": "assets/icon32.png",
      "48": "assets/icon48.png",
      "128": "assets/icon128.png"
    }
  },
  "side_panel": {
    "default_path": "sidepanel/sidepanel.html"
  },
  "content_scripts": [
    {
      "matches": [
        "https://www.espn.com/fantasy/football*",
        "https://fantasy.espn.com/football*"
      ],
      "js": [
        "content/detector.js"
      ],
      "css": [
        "content/detector.css"
      ],
      "run_at": "document_idle"
    },
    {
      "matches": [
        "https://fantasy.nfl.com/*",
        "https://fantasyfootball.nfl.com/*"
      ],
      "js": [
        "content/nfl-detector.js"
      ],
      "css": [
        "content/detector.css"
      ],
      "run_at": "document_idle"
    },
    {
      "matches": [
        "https://sleeper.com/*",
        "https://sleeper.app/*"
      ],
      "js": [
        "content/sleeper-auth.js"
      ],
      "run_at": "document_idle"
    }
  ],
  "web_accessible_resources": [
    {
      "resources": [
        "assets/app_logo.png",
        "assets/icon32.png"
      ],
      "matches": [
        "https://www.espn.com/*",
        "https://fantasy.espn.com/*",
        "https://fantasy.nfl.com/*",
        "https://fantasyfootball.nfl.com/*"
      ]
    }
  ],
  "icons": {
    "16": "assets/icon16.png",
    "32": "assets/icon32.png",
    "48": "assets/icon48.png",
    "128": "assets/icon128.png"
  }
}