Add crates.io badge

Author: wjakobczyk

README.md

@@ -637,7 +637,7 @@ Work in progress drivers. Help the authors make these crates awesome!
 1. [MCP49xx] - SPI - 8/10/12-bit DACs like MCP4921, MCP4922, MCP4801, etc. - ![crates.io](https://img.shields.io/crates/v/mcp49xx.svg)
 1. [MCP9808] - I2C - Temperature sensor - ![crates.io](https://img.shields.io/crates/v/mcp9808.svg)
 1. [MFRC522] - SPI - RFID tag reader/writer
-1. [midi-port] - UART - MIDI input
+1. [midi-port] - UART - MIDI input - ![crates.io](https://img.shields.io/crates/v/midi-port.svg)
 1. [motor-driver] - Motor drivers: L298N, TB6612FNG, etc.
 1. [MPU6050] - I2C - no_std driver for the MPU6050 ![crates.io](https://img.shields.io/crates/v/mpu6050.svg)
 1. [MPU9250] - no_std driver for the MPU9250 (and other MPU* devices) & onboard AK8963 (accelerometer + gyroscope +  magnetometer IMU) ![crates.io](https://img.shields.io/crates/v/mpu9250.svg)