* handwired/promethium: refactor
- config.h files
- updated to use #pragma once
- removed redundant config.h includes
- layout macro moved from config.h to promethium.h
- layout macro renamed from KEYMAP_CUSTOM to LAYOUT
* handwired/promethium: Configurator support
* Remove chording as it is not documented, not used, and needs work.
* Make Leader Key an optional feature.
* Switch from `PREVENT_STUCK_MODIFIERS` to `STRICT_LAYER_RELEASE`
* Remove `#define PREVENT_STUCK_MODIFIERS` from keymaps.
