Examine source code of Twitch Volume Scroll

{
  "manifest_version": 3,
  "name": "Twitch Volume Scroll",
  "version": "1.0.0",
  "description": "Right-click and scroll on the Twitch player to adjust volume, with an on-screen indicator.",
  "permissions": [
    "storage"
  ],
  "content_scripts": [
    {
      "matches": [
        "*://*.twitch.tv/*"
      ],
      "js": [
        "content.js"
      ],
      "run_at": "document_idle",
      "all_frames": true
    }
  ],
  "action": {
    "default_popup": "popup.html",
    "default_title": "Twitch Volume Scroll"
  },
  "options_ui": {
    "page": "options.html",
    "open_in_tab": false
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "twitch-volume-scroll@local",
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      }
    }
  }
}