Examine source code of MC Converter

{
  "manifest_version": 3,
  "name": "mc converter",
  "version": "1.0",
  "description": "Converts meters to centimeters and vice versa",
  "action": {
    "default_popup": "popup.html"
  },
  "icons": {
    "16": "icon16.png",
    "48": "icon48.png",
    "128": "icon.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "your@unique.extension.id"
    }
  }
}