Examine source code of Monstercat Player

{
  "manifest_version": 2,
  "name": "Monstercat Player",
  "version": "1.1.4",
  "description": "Provides a browser wide player for your favorite songs!",
  "applications": {
    "gecko": {
      "id": "McatPlayerRelease@dvsproductions.de"
    }
  },
  "icons": {
    "48": "icons/icon.svg",
    "96": "icons/icon.svg"
  },
  "permissions": [
    "*://*.monstercat.com/*",
    "activeTab",
    "tabs",
    "storage",
    "downloads"
  ],
  "browser_action": {
    "default_area": "navbar",
    "default_icon": "icons/icon.svg",
    "default_title": "Monstercat Player [DEBUG]",
    "default_popup": "popup/frontend.html"
  },
  "content_scripts": [
    {
      "matches": [
        "*://*.monstercat.com/*"
      ],
      "js": [
        "Player.js"
      ],
      "run_at": "document_idle"
    }
  ],
  "background": {
    "scripts": [
      "Backend.js"
    ]
  },
  "options_ui": {
    "page": "options/options.html",
    "browser_style": true
  }
}