Adds the mqtt-sn to the list of no-std crates

README.md

@@ -893,6 +893,7 @@ Work in progress drivers. Help the authors make these crates awesome!
 1. [irq](https://crates.io/crates/irq): utilities for writing interrupt handlers (allows moving data into interrupts, and sharing data between them) - ![crates.io](https://img.shields.io/crates/v/irq.svg)
 1. [managed](https://crates.io/crates/managed): provides `ManagedSlice`, `ManagedMap` backed by either their std counterparts or fixed-size buffers for `#![no_std]`. - ![crates.io](https://img.shields.io/crates/v/managed.svg)
 1. [menu]: A basic command-line interface library. Has nested menus and basic help functionality. ![crates.io](https://img.shields.io/crates/v/menu.svg)
+1. [mqtt-sn](https://crates.io/crates/mqtt-sn): Implementation of the MQTT-SN protocol - ![crates.io](https://img.shields.io/crates/v/mqtt-sn.svg)
 1. [microfft](https://crates.io/crates/microfft): Embedded-friendly (`no_std`, no-`alloc`) fast fourier transforms - ![crates.io](https://img.shields.io/crates/v/microfft.svg)
 1. [micromath](https://github.com/NeoBirth/micromath): Embedded Rust math library featuring fast, safe floating point approximations for common arithmetic operations, 2D and 3D vector types, and statistical analysis - ![crates.io](https://img.shields.io/crates/v/micromath.svg)
 1. [nalgebra](https://crates.io/crates/nalgebra): general-purpose and low-dimensional linear algebra library - ![crates.io](https://img.shields.io/crates/v/nalgebra.svg)