Implement `keyboard.json` for `dumbpad/v3x`

keyboards/dumbpad/v3x/rules.mk

@@ -1,16 +0,0 @@
-# Build Options
-#   change yes to no to disable
-#
-BOOTMAGIC_ENABLE = yes      # Enable Bootmagic Lite
-MOUSEKEY_ENABLE = no       # Mouse keys
-EXTRAKEY_ENABLE = yes       # Audio control and System control
-CONSOLE_ENABLE = no         # Console for debug
-COMMAND_ENABLE = no         # Commands for debug and configuration
-NKRO_ENABLE = no           # Enable N-Key Rollover
-BACKLIGHT_ENABLE = no       # Enable keyboard backlight functionality
-RGBLIGHT_ENABLE = no        # Enable keyboard RGB underglow
-AUDIO_ENABLE = no           # Audio output
-
-ENCODER_ENABLE = yes
-
-RGB_MATRIX_ENABLE = yes