Examine source code of Tab Volume Mixer & Booster

{
  "manifest_version": 3,
  "name": "Tab Volume Mixer & Booster",
  "version": "1.2.2",
  "description": "Independent volume control per tab (slider 0-600%), volume booster, media controls, and mute extension for Firefox.",
  "author": "Developer",
  "permissions": [
    "tabs",
    "scripting",
    "activeTab",
    "storage"
  ],
  "host_permissions": [
    "<all_urls>"
  ],
  "action": {
    "default_popup": "popup/popup.html",
    "default_icon": "icons/icon.svg",
    "default_title": "Tab Volume Mixer"
  },
  "icons": {
    "16": "icons/icon16.png",
    "48": "icons/icon48.png",
    "128": "icons/icon128.png"
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "content.js"
      ],
      "run_at": "document_idle",
      "all_frames": true
    }
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "tab-volume-mixer@extension.local",
      "strict_min_version": "109.0",
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      }
    }
  }
}