README: Add SPI Flash driver to be implemented

For HiFive1 are be all usefull we need implement
SPI Flash driver to save and run code without have to
open terminal.

This is alpha relese 2v00.142

Signed-off-by: Matheus Castello <matheus@castello.eng.br>

README.md

@@ -90,6 +90,7 @@ If you are a board manufacturer interested in getting your board officially supp
 		* PWM
 		* I2C
 		* GPIO IRQs "pin watch"
+		* SPI Flash Driver
 * [Original Espruino Board](http://www.espruino.com/EspruinoBoard) - great support.
 * [Espruino Pico Board](http://www.espruino.com/Pico) - great support.
 * [Puck.js](http://www.espruino.com/Puck.js) - great support.