Add DIO example to master

[nitin710]

• merge digital input logging example #263 into master
• Needs
  • a fix for ESP32 hardware interrupt system
    • Currently we poll for GPIO state in the main loop
• Needs testing on both SAMD and ESP

[nitin710]

• Maybe using a doubleBuffer for DIO.
• This way, an interrupt will populate (time, pulse) in the IN buffer and the mainloop can access the OUT buffer.
  • Resolves any access violations.