Planck PCB Rev 6.1

Update: the PCBs have arrived. Shipping has begun.  This is a group buy for a batch of PCBs produced through Drop's sources, and is expected to be delivered in December 2020. It is the same design as done previously, but with more testing. Small changes are highlighted below in bold. The group buy will run until Oct 1st. STM32F303 ARM MCU USB-C connector ESD protection on the USB datalines Dual-channel speaker using the MCU's DAC Kailh's hot-swappable MX sockets and solderable Matias footprint Metal 2.5mm standoffs that accept M2 screws Per-switch RGB cut-outs for future projects (no LED support otherwise) Compatible with previous revision case styles 2x2u, 1x2u, Grid support along the bottom row PCB-mounted stabiliser footprints 9x soldered-on WS2812B RGB LEDs Footprints for add-ons to expand functionality: Footprint for a 4-channel DIP switch (210-4ES) Footprint for a 2-pin JST-PH (PRT-09749) Footprint for a 4-pin Qwiic (I2C) JST-SH connector (PRT-14417) making it compatible with