Examine source code of Simple Sound Control

{
  "manifest_version": 3,
  "browser_specific_settings": {
    "gecko": {
      "id": "simple-sound-control@ssc.craftxlogic.com",
      "strict_min_version": "140.0",
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      }
    }
  },
  "name": "Simple Sound Control",
  "version": "0.2.6",
  "description": "Per-tab volume boost and quick levels in a clean UI popup. Ad-free.",
  "icons": {
    "16": "icon-16.png",
    "32": "icon-32.png",
    "48": "icon-48.png",
    "128": "icon-128.png"
  },
  "action": {
    "default_popup": "popup.html",
    "default_title": "Simple Sound Control",
    "default_icon": {
      "16": "icon-16.png",
      "32": "icon-32.png",
      "48": "icon-48.png",
      "128": "icon-128.png"
    }
  },
  "permissions": [
    "storage",
    "tabs"
  ],
  "host_permissions": [
    "http://*/*",
    "https://*/*"
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "content_scripts": [
    {
      "matches": [
        "http://*/*",
        "https://*/*"
      ],
      "js": [
        "content.js"
      ],
      "run_at": "document_idle",
      "all_frames": true
    }
  ],
  "content_security_policy": {
    "extension_pages": "script-src 'self'; object-src 'self'; style-src 'self'; img-src 'self' data:; font-src 'self'"
  }
}