* [BACKLIGHT_CAPS_LOCK_INDICATOR] Use backlight toggling as Caps Lock LED
I've implemented this feature because S65-X doesn't have LED indicators
and the existing led_set_kb(usb_led) function try to use backlight as
indicator but that creates an inconsistency with backlight_config state.
- define `BACKLIGHT_CAPS_LOCK_INDICATOR` to enable Caps Lock indicator
using backlight (for keyboards without dedicated LED)
- Don't turn off LED indicators when suspend because backlight is
already turned off. Else led_set(0) will turn back on backlight.
- Documentation has been updated
* [BACKLIGHT_CAPS_LOCK_INDICATOR] Turn off all LED indicators except Caps Lock if BACKLIGHT_CAPS_LOCK_INDICATOR
* [BACKLIGHT_CAPS_LOCK] Rename BACKLIGHT_CAPS_LOCK_INDICATOR
* [BACKLIGHT_CAPS_LOCK] Use new IS_LED_ON method