Support for SDMMC interface instead of SPI for SD card

[Maxim88S]

Hello! Thank you for the great project.

Currently, the SD card communication appears to be implemented using the SPI interface. I would like to know if it is possible to switch it to the SDMMC interface.
Is SDMMC mode currently supported or configurable?

[jgauchia]

Hello,
Thank you.

It's not currently implemented, but I could look into adding SDMMC support and making it configurable via flags in platformio.ini.

My device doesn't have enough GPIO pins to test it, but I could build a small prototype board to try and add support.

I'll make a note of it and get back to you as soon as possible.