[Core] Tri Layer Keys (#19795)

Co-authored-by: wilba <wilba@wilba.tech>
Co-authored-by: Pablo Martínez <58857054+elpekenin@users.noreply.github.com>
Co-authored-by: Joel Challis <git@zvecr.com>
Co-authored-by: Nick Brassel <nick@tzarc.org>

builddefs/common_features.mk

@@ -620,6 +620,7 @@ ifeq ($(strip $(VIA_ENABLE)), yes)
     DYNAMIC_KEYMAP_ENABLE := yes
     RAW_ENABLE := yes
     BOOTMAGIC_ENABLE := yes
+    TRI_LAYER_ENABLE := yes
     SRC += $(QUANTUM_DIR)/via.c
     OPT_DEFS += -DVIA_ENABLE
 endif

builddefs/generic_features.mk

@@ -39,6 +39,7 @@ GENERIC_FEATURES = \
     VELOCIKEY \
     WPM \
     DYNAMIC_TAPPING_TERM \
+    TRI_LAYER
 
 define HANDLE_GENERIC_FEATURE
     # $$(info "Processing: $1_ENABLE $2.c")

builddefs/show_options.mk

@@ -84,7 +84,8 @@ OTHER_OPTION_NAMES = \
   PROGRAMMABLE_BUTTON_ENABLE \
   SECURE_ENABLE \
   CAPS_WORD_ENABLE \
-  AUTOCORRECT_ENABLE
+  AUTOCORRECT_ENABLE \
+  TRI_LAYER_ENABLE
 
 define NAME_ECHO
        @printf "  %-30s = %-16s # %s\\n" "$1" "$($1)" "$(origin $1)"