[Keyboard] boardsource/3x4 data driven (#17628)

* initial

* change to development board

* replaced KC_TRNS & use rules.mk template

keyboards/boardsource/3x4/rules.mk

@@ -1,17 +1 @@
-# MCU name
-MCU = atmega32u4
-
-# Bootloader selection
-BOOTLOADER = caterina
-
-# Build Options
-#   change yes to no to disable
-#
-BOOTMAGIC_ENABLE = yes      # Enable Bootmagic Lite
-MOUSEKEY_ENABLE = yes       # Mouse keys
-EXTRAKEY_ENABLE = yes       # Audio control and System control
-CONSOLE_ENABLE = yes        # Console for debug
-COMMAND_ENABLE = yes        # Commands for debug and configuration
-NKRO_ENABLE = no            # Enable N-Key Rollover
-BACKLIGHT_ENABLE = no       # Enable keyboard backlight functionality
-AUDIO_ENABLE = no           # Audio output
+# This file intentionally left blank