give track some more space to the cutout

bump revision to v2020-06-23

silkscreen: mark teensy++ do not connect pins with x

silkscreen: add rectangle for adding own marker descriptions

silkscreen: mark LED cathodes very explicitly

switch from 0R resistors to solder jumpers (thanks mxf)

teensy: add teensy++ 2.0 RST/GND/5V pins in correct spot They differ by one pin between the 3.x series and the teensy++.

fix top mounting hole: was 5mm, should be 6mm

move right_13_down and left_13_lt a few millimeters up For less strain on the FPC cables, on both KB500 and KB600.

README: describe possible teensy combinations