Examine source code of Tube2Spot

{
  "name": "Tube2Spot",
  "manifest_version": 2,
  "description": "Tube2Spot is a straightforward Firefox extension that allows you to effortlessly add songs from YouTube to your Spotify playlists.",
  "version": "0.1",
  "page_action": {
    "default_icon": "assets/icons/icon128.png",
    "default_popup": "popup.html",
    "default_title": "Tube2Spot"
  },
  "icons": {
    "16": "assets/icons/icon16.png",
    "32": "assets/icons/icon32.png",
    "48": "assets/icons/icon48.png",
    "128": "assets/icons/icon128.png"
  },
  "permissions": [
    "tabs",
    "storage"
  ],
  "content_scripts": [
    {
      "matches": [
        "*://*.youtube.com/*"
      ],
      "js": [
        "content.js"
      ]
    },
    {
      "matches": [
        "*://*.youtube.com/?code*"
      ],
      "run_at": "document_start",
      "js": [
        "libs/oauth/injection.js"
      ]
    }
  ],
  "background": {
    "scripts": [
      "background.js"
    ],
    "persistent": false
  },
  "web_accessible_resources": [
    "libs/*/*"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{87c4ea0b-774d-4ef3-9850-a6b32a270e3b}"
    }
  }
}