Examine source code of MP3Juices.mu

{
  "manifest_version": 3,
  "name": "MP3Juices",
  "version": "1.0",
  "homepage_url": "https://mp3juices.mu/",
  "description": "This Add-On adds a shortcut to download and convert Videos to MP3 (audio) or MP4 (video) on MP3Juices.",
  "icons": {
    "32": "icons/32.png",
    "48": "icons/48.png",
    "64": "icons/64.png",
    "128": "icons/128.png"
  },
  "browser_action": {
    "default_icon": "icons/32.png",
    "default_title": "MP3Juices",
    "default_popup": "popup/index.html"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "firefox@mp3juices.mu"
    }
  },
  "permissions": [
    "tabs",
    "activeTab"
  ]
}