Examine source code of no-direct-ip

{
  "description": "Block directly entered, external or public IP v4 and v6 addresses",
  "manifest_version": 2,
  "name": "no-direct-ip",
  "version": "0.3.0",
  "homepage_url": "https://github.com/OllieJC/no-direct-ip",
  "icons": {
    "48": "icons/block.svg",
    "96": "icons/block.svg"
  },
  "permissions": [
    "webRequest",
    "webRequestBlocking",
    "<all_urls>",
    "search",
    "storage"
  ],
  "background": {
    "page": "background/page.html"
  },
  "options_ui": {
    "page": "resources/options.html",
    "browser_style": true
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{d43fcf27-0a5c-4c1e-9847-f22d0bb0b4d4}",
      "strict_min_version": "68.0"
    }
  },
  "web_accessible_resources": [
    "resources/*",
    "icons/*"
  ]
}