* Helix each keymap's using rgblight mode symbol instead magic number
No change in build result.
* Helix pico keymaps: make rgblight modes selectable.
No change in build result.
* Helix rev2 keymaps: make rgblight modes selectable.
No change in build result.
* fixed Helix froggy/keymap.c: invalid rgblight mode value 0 to 1 (=RGBLIGHT_MODE_STATIC_LIGHT)
* Deselect RGB_TEST and ALTERNATING in Helix rev2,pico keymaps config.h.
* 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.
