Feature request: Add INPUT_PULLDOWN support to pinPeripheral()

The pinPeripheral() function in wiring_private.c has support for "PIO_INPUT", "PIO_INPUT_PULLUP" and "PIO_OUTPUT". It lacks support for the "PULL DOWN" configuration.

Interestingly, pinMode() does support "INPUT_PULLDOWN".

I propose that we add:

if ( ulPeripheral == PIO_INPUT_PULLDOWN )
{
pinMode( ulPin, INPUT_PULLDOWN ) ;
}

We will also need to add PIO_INPUT_PULLDOWN to the EPioType in WVariant.h.

I would be happy to submit a PR for this. Before I do, I have one question regarding suggestions of how best to set up my environment to use the ArduinoCore-samd Git repo instead of the core that is installed with the IDE.

Start with wiring_private.c to review how pinPeripheral() handles the existing PIO_INPUT and PIO_INPUT_PULLUP cases, then inspect EPioType in WVariant.h. Confirm the existing pinMode() INPUT_PULLDOWN support and ensure the new peripheral type is recognized; the work is done when both files support INPUT_PULLDOWN consistently.

Written by the indexing model from the issue text.