* clean up rgb matrix extern usage

Moved rgb matrix boiler plate into macros

Rebased onto typing heatmap pr

* Fixing the reversed frame buffer access in digital rain

* Fixing digital rain & typing heatmap if keyreactive effects are not enabled

* Apply suggestions from code review

Co-Authored-By: Drashna Jaelre <[email protected]>

* Adding parenthesizes to DRIVER_LED_TOTAL where necessary

* Updated docs

* added notes about parentheses