Examine source code of Grubby Grub

{
  "manifest_version": 3,
  "name": "Grubby Grub",
  "version": "1.2",
  "description": "Adds the UK Food Hygiene Rating to restaurant listings in Google Maps.",
  "icons": {
    "48": "icons/48.png",
    "96": "icons/96.png",
    "128": "icons/128.png"
  },
  "content_scripts": [
    {
      "matches": [
        "https://www.google.co.uk/maps*",
        "https://www.google.com/maps*"
      ],
      "js": [
        "foodHygieneInjector.js"
      ]
    }
  ],
  "host_permissions": [
    "https://api.ratings.food.gov.uk/*"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{f2155886-59d4-426c-8a68-2bc065a33410}"
    }
  }
}