Add details & example to the README

Author: pimterry

README.md

@@ -1,2 +1,33 @@
-# usbmux-client
-A pure-js Node.js library for communicating with iPhones over USB via usbmux
+# Usbmux-Client [![Build Status](https://github.com/httptoolkit/usbmux-client/workflows/CI/badge.svg)](https://github.com/httptoolkit/usbmux-client/actions) [![Available on NPM](https://img.shields.io/npm/v/usbmux-client.svg)](https://npmjs.com/package/usbmux-client)
+
+> _Part of [HTTP Toolkit](https://httptoolkit.com): powerful tools for building, testing & debugging HTTP(S)_
+
+A pure-js Node.js library for communicating with iPhones over USB via usbmux, with a pure-JS solution for Node.js that works on all platforms.
+
+This provides fully cross-platform access to iOS devices, supporting the usbmuxd daemon built into iTunes on Windows & Mac, and the libimobiledevice implementation on Linux.
+
+This is used within HTTP Toolkit to connect to TCP ports on a connected iPhone via USB, primarily to communicate with Frida using [Frida-JS](https://github.com/httptoolkit/frida-js/). It's currently focused on the core features required for that use case, but PRs to add support for more features are welcome. Right now it supports:
+
+* Monitoring the list of connected devices
+* Querying the metadata for any connected device (to get the device name, device type, UDID, architecture, etc)
+* Opening a direct connection to any port on the device itself
+
+## Example
+
+```javascript
+import { UsbmuxClient } from 'usbmux-client';
+
+const client = new UsbmuxClient();
+
+const devices = await client.getDevices();
+// Returns a map from id to basic data like {
+//   "1": { ConnectionType: "USB", DeviceId: "1", ... }
+// }
+
+const firstDeviceId = Object.keys(devices)[0];
+const deviceMetadata = await client.queryAllDeviceValues(firstDeviceId);
+// Returns detailed data like { DeviceClass: "iPhone", DeviceName: "Alice's iPhone", ... }
+
+// Returns a net.Socket connected to the given port on the target device:
+const conn = await client.createDeviceTunnel(firstDeviceId, 1234);
+```