Examine source code of Audio Booster

{
  "manifest_version": 2,
  "name": "Audio Booster",
  "version": "1.0.0",
  "description": "Boost audio beyond 100% on any tab",
  "browser_specific_settings": {
    "gecko": {
      "id": "audio-booster@extension",
      "strict_min_version": "140.0",
      "data_collection_permissions": {
        "required": [
          "none"
        ],
        "optional": []
      }
    }
  },
  "permissions": [
    "activeTab",
    "scripting",
    "storage",
    "tabs",
    "alarms",
    "<all_urls>"
  ],
  "icons": {
    "16": "icon16.png",
    "32": "icon32.png",
    "48": "icon48.png",
    "128": "icon128.png"
  },
  "browser_action": {
    "default_popup": "popup.html",
    "default_title": "Audio Booster",
    "default_icon": {
      "16": "icon16.png",
      "32": "icon32.png",
      "48": "icon48.png",
      "128": "icon128.png"
    }
  },
  "background": {
    "scripts": [
      "background.js"
    ],
    "persistent": false
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "content.js"
      ],
      "run_at": "document_idle"
    }
  ]
}