Add support for attiny1624

PCB for ATTiny1624. Does not obsolete the attiny841 version, just hel…

…ps with supply chain issues. Requires UPDI programmer, will NOT work with classic AVR/ISP programmers (usbtinyisp/etc)

Adds two SMD pads for up/down buttons. C668117

Fix intermittent beeping when audio feedback mode is enabled

September firmware release

v6 (pcb only)

v6 gerbers

Merge branch 'overshoot'

Flashing script