Examine source code of ValueChecker

{
  "manifest_version": 3,
  "name": "Grayscale!",
  "version": "1.0",
  "description": "Toggle accurate dot dain 20% grayscale on images and videos.",
  "permissions": [
    "storage",
    "activeTab"
  ],
  "action": {
    "default_popup": "popup.html",
    "default_icon": "icon-gray.png"
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "css": [
        "content.css"
      ],
      "js": [
        "content.js"
      ],
      "run_at": "document_end"
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "grayscalefirefox@akabi",
      "data_collection_permissions": {
        "required": [
          "none"
        ],
        "optional": []
      }
    }
  }
}