Understanding QMK’s Code
https://docs.qmk.fm/#/custom_matrix
Debouncing in QMK https://docs.qmk.fm/#/feature_debounce_type
https://docs.qmk.fm/#/syllabus
https://github.com/qmk/qmk_firmware
https://docs.qmk.fm/#/newbs_learn_more_resources