documentation: Add USB/IP server and client

docs/configuration/service/usbip-client.md

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+---
+icon: material/new-box
+---
+
+!!! question "Since sing-box 1.14.0"
+
+# USB/IP Client
+
+USB/IP Client service imports remote USB devices over [USB/IP](https://usbip.sourceforge.net/),
+exported by the [USB/IP Server](/configuration/service/usbip-server/).
+
+Available on Linux, Windows, and macOS (macOS requires a build with CGO). Not available on iOS.
+
+The server must be a sing-box (or sing-usbip) server.
+
+### Structure
+
+```json
+{
+  "type": "usbip-client",
+
+  ... // Dial Fields
+
+  "server": "",
+  "server_port": 0,
+  "devices": []
+}
+```
+
+!!! info "Difference from the official USB/IP protocol"
+
+    sing-box uses [sing-usbip](https://github.com/SagerNet/sing-usbip), which uses an additional
+    set of protocols to support enhancements such as hotplug, while remaining interoperable with
+    the standard USB/IP protocol.
+
+### Dial Fields
+
+See [Dial Fields](/configuration/shared/dial/) for details.
+
+Only `detour` takes effect.
+
+### Fields
+
+#### server
+
+==Required==
+
+The remote `usbip-server` address.
+
+#### server_port
+
+The remote `usbip-server` port. Defaults to `3240`.
+
+#### devices
+
+List of device matches selecting which remote devices to import. If empty, all exported devices
+are imported.
+
+Object format:
+
+```json
+{
+  "bus_id": "",
+  "vendor_id": 0,
+  "product_id": 0,
+  "serial": ""
+}
+```
+
+Object fields:
+
+- `bus_id`: USB bus ID, e.g. `1-2`.
+- `vendor_id`: USB vendor ID, as a number.
+- `product_id`: USB product ID, as a number.
+- `serial`: Device serial number.
+
+Within one object, all specified fields must match; multiple objects are combined as a union. At
+least one field is required.