SD card formatting tool

[iandinwoodie]

Overview

This patch adds an SD card formatting tool (SDFmt) that formats the currently inserted SD card using the ESP32 Arduino framework's SD card library.

Rationale

I had recently ordered some 256MB SD cards (Class 4) to use with the CYD. The CYD was unable to utilize the SD card and produced the following error:

[    46][E][sd_diskio.cpp:806] sdcard_mount(): f_mount failed: (13) There is no valid FAT volume

I attempted to remedy the situation by formatting the card with the following tools:

• Windows Disk Management
• macOS Disk Utility
• SD Association SD Card Formatter

Regardless, the card continued to fail to mount with the no valid FAT volume error message. However, I was able to remedy the situation using the format_if_empty flag of the SDFS::begin method. The caveat of this solution is that the resulting formatted card can be utilized by the CYD, but none of the other platforms recognize it as a valid format.

I think this is a worthwhile addition to the CYD collection for users seeking out smaller capacity SD cards that may run into the same scenario.

[iandinwoodie]

Also, please let me know if you would like the project moved to a different location. I added it to a new top-level Tools directory because it is not necessarily an example and I wasn't sure of a better location for it.