Update readme.md

The matrix_col_t type was added in commit 0284431 (part of qmk#3449),
but then the code which used that type was removed in qmk#6140, and no
other users were added since that time.  The presence of that type,
however, limits MATRIX_ROWS to 32, which probably does not matter for a
real keyboard, but prevents doing things like making a firmware to test
all existing pins on a board like Teensy++ 2.0 (which has 46 GPIOs).

* Add support for soft serial to ATmega32U2

* Update drivers/avr/serial.c

* Update drivers/avr/serial.c

* Update drivers/avr/serial.c

* Fix comment

* Update drivers/avr/serial.c

…ty value (qmk#9940)

* Initial changes to expose "real" MIDI velocity

* Change MI_VELU and MI_VELD to fit new logic

* Apply cleanups from fauxpark's review

my bad on the errant whitespace and else {} placements

* Slight changes to MI_VELD to match values when velocity is falling to when it is rising

* Add keycode MI_VEL_0

* Update compute_velocity() to handle MI_VEL_0

* Store velocity as 7 bits to hard cap value at 127

Not adding them at the end of the list apparently risks breaking
compatibility with VIA.

Source: qmk#9703 (comment)