[Library Manager] Adafruit_SPIFlash

[ladyada]

hello! i have a new library that makes SPI flash filesystems ez and fun :)

https://github.com/adafruit/Adafruit_SPIFlash

release 1.0.0
https://github.com/adafruit/Adafruit_SPIFlash/releases/tag/1.0.0

thank u!

[cmaglie]

Done!