Update Documentation

[MattyBoy4444]

Another method to get the latest for Windows

1. Download latest zip from 'WiFi101 Firmware Updater' which should include the latest nina-fw
   https://github.com/arduino/WiFi101-FirmwareUpdater-Plugin

2. Unzip and copy the WiFi101 folder to 'C:\Program Files (x86)\Arduino\tools'

3. reopen Arduino IDE