Examine source code of ListenTogether for Youtube Music

{
  "manifest_version": 2,
  "name": "__MSG_appName__",
  "description": "__MSG_appDescription__",
  "version": "1.0.5",
  "icons": {
    "16": "icons/lt-16.png",
    "32": "icons/lt-32.png",
    "48": "icons/lt-48.png",
    "96": "icons/lt-96.png",
    "128": "icons/lt-128.png"
  },
  "default_locale": "en",
  "permissions": [
    "storage",
    "tabs"
  ],
  "web_accessible_resources": [
    "whats-new.json",
    "icons/lt-16.png",
    "content-scripts/content.css"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{a65ba25f-8a24-4217-a5f3-55be05bdf507}",
      "data_collection_permissions": {
        "required": [
          "none"
        ],
        "optional": [
          "technicalAndInteraction"
        ]
      }
    }
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "browser_action": {
    "default_title": "ListenTogether",
    "default_popup": "popup.html"
  },
  "content_scripts": [
    {
      "matches": [
        "https://music.youtube.com/*"
      ],
      "js": [
        "content-scripts/content.js"
      ]
    },
    {
      "matches": [
        "https://music.youtube.com/*"
      ],
      "run_at": "document_idle",
      "js": [
        "content-scripts/player-bridge.js"
      ],
      "world": "MAIN"
    },
    {
      "matches": [
        "https://listentogether.now/*"
      ],
      "run_at": "document_idle",
      "js": [
        "content-scripts/site.js"
      ]
    }
  ]
}