Examine source code of Volume Control

{
  "manifest_version": 2,
  "name": "Volume Control",
  "version": "1.0",
  "description": "Control the volume of audio and video on any page",
  "permissions": [
    "activeTab",
    "storage",
    "tabs"
  ],
  "browser_action": {
    "default_popup": "popup.html",
    "default_title": "Volume Control",
    "default_icon": {
      "48": "icon.svg"
    }
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "content.js"
      ],
      "run_at": "document_start"
    }
  ],
  "web_accessible_resources": [
    "inject.js"
  ],
  "icons": {
    "48": "icon.svg"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{a3f82d1e-7c4b-4e9a-b2d5-6f1c8e3a0d7f}",
      "strict_min_version": "142.0",
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      }
    }
  }
}