create README

Author: zefir-git

README.md

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+# @cldn/ip
+
+IP address utility.
+
+## Features
+
+- Works in the browser and in Node.js without any polyfills. (A bundler like Webpack or Vite is recommended for the
+    browser)
+- IPv4 and IPv6 classes.
+- Get IP address as BigInt, binary or string.
+- Extract IPv4-mapped IPv6 addresses.
+- Subnet class with methods to check IP membership, create netmask, list addresses, etc.
+- Network class for working with multiple subnets.
+- Written in TypeScript.
+
+See the [**Documentation**](https://ip.cldn.pro)
+
+## Installation
+
+```sh
+npm install @cldn/ip
+```
+
+## Usage
+
+```ts
+import {IPv4, IPv6, Subnet} from "@cldn/ip";
+
+const ipv6 = IPv4.fromString("::ffff:192.168.1.42");
+const ipv4 = ipv6.getMappedIPv4();
+
+const subnet = Subnet.fromString("192.168.0.0/16");
+subnet.has(ipv4); // true
+```
+
+## Licence
+
+Copyright © 2024 Cloudnode OÜ
+
+This file is part of @cldn/ip.
+
+@cldn/ip is free software: you can redistribute it and/or modify it under the terms of the GNU Lesser General
+Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any
+later version.
+
+@cldn/ip is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied
+warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more
+details.