Examine source code of YouTrack

{
  "manifest_version": 2,
  "name": "YouTrack",
  "description": "YouTrack, your better YouTube Music playlist management system.",
  "version": "1.0.6",
  "icons": {
    "16": "/icons/youtrack_orange_16.png",
    "32": "/icons/youtrack_orange_32.png",
    "48": "/icons/youtrack_orange_48.png",
    "128": "/icons/youtrack_orange_128.png"
  },
  "permissions": [
    "storage",
    "https://api.youtrack.site/"
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "browser_action": {
    "default_title": "YouTrack",
    "default_popup": "popup.html"
  },
  "content_scripts": [
    {
      "matches": [
        "https://youtrack.site/*"
      ],
      "run_at": "document_start",
      "js": [
        "content-scripts/youtrack.js"
      ]
    },
    {
      "matches": [
        "https://music.youtube.com/*"
      ],
      "run_at": "document_idle",
      "css": [
        "content-scripts/youtube.css"
      ],
      "js": [
        "content-scripts/youtube.js"
      ]
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{4000dc7e-46e7-4727-847c-b47b6870b52c}"
    }
  }
}