add natiu-mqtt (#5261)

README.md

@@ -1946,6 +1946,7 @@ _Libraries for working with various layers of the network._
 - [llb](https://github.com/kirillDanshin/llb) - It's a very simple but quick backend for proxy servers. Can be useful for fast redirection to predefined domain with zero memory allocation and fast response.
 - [mdns](https://github.com/hashicorp/mdns) - Simple mDNS (Multicast DNS) client/server library in Golang.
 - [mqttPaho](https://eclipse.org/paho/clients/golang/) - The Paho Go Client provides an MQTT client library for connection to MQTT brokers via TCP, TLS or WebSockets.
+- [natiu-mqtt](https://github.com/soypat/natiu-mqtt) - A dead-simple, non-allocating, low level implementation of MQTT well suited for embedded systems.
 - [nbio](https://github.com/lesismal/nbio) - Pure Go 1000k+ connections solution, support tls/http1.x/websocket and basically compatible with net/http, with high-performance and low memory cost, non-blocking, event-driven, easy-to-use.
 - [netpoll](https://github.com/cloudwego/netpoll) - A high-performance non-blocking I/O networking framework, which focused on RPC scenarios, developed by ByteDance.
 - [NFF-Go](https://github.com/intel-go/nff-go) - Framework for rapid development of performant network functions for cloud and bare-metal (former YANFF).