Add modifier state to the split keyboard transport (#10400)

* Add modifier state to the split transport

This adds modifier state to the i2c and serial transport for split
keyboards.  The purpose of this is to allow e.g. displaying modifier
state on the slave side of a split keyboard on an oled.  This adds one
byte to the data transferred between halves.

This also fixes a missing ifdef guard for BLACKLIGHT_ENABLE.

Break modifiers into real/weak/oneshot

Fix incorrect slave serial mod setting

Fix typo in serial weal mod setter

Fix build errors for the I2C code that I introduced

Code cleanup and formatting per project preferences

Correctly get oneshot mods

Fix missing braces

Remove unneeded ifdef guard

Make the added state transport optional

Add documentation for the new define to enable this feature

Fix stray grave mark

* Fix error introduced in conflict resolution

0 files changed, 0 insertions, 0 deletions