Examine source code of AutoScroll Plus

{
  "manifest_version": 3,
  "name": "Middle Button Scroll",
  "version": "1.0.1",
  "description": "Enables Windows-style middle button scrolling",
  "icons": {
    "48": "icon48.png",
    "128": "icon128.png"
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "browser-polyfill.js",
        "content.js"
      ],
      "run_at": "document_start"
    }
  ],
  "background": {
    "service_worker": "background_wrapper.js",
    "scripts": [
      "browser-polyfill.js",
      "background-script.js"
    ]
  },
  "permissions": [
    "storage"
  ],
  "web_accessible_resources": [
    {
      "resources": [
        "browser-polyfill.js"
      ],
      "matches": [
        "<all_urls>"
      ]
    }
  ],
  "action": {
    "default_popup": "popup.html",
    "default_icon": {
      "48": "icon48.png"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "sundancegithub@gmail.com"
    }
  },
  "content_security_policy": {
    "extension_pages": "script-src 'self'; object-src 'self'"
  }
}