[Keyboard] add YMDK YMD21 v2 (#16442)

* [Keyboard] add YMDK YMD21 v2

* remove trailing whitespace from default keymap

keyboards/ymdk/ymd21/v2/rules.mk

@@ -0,0 +1,20 @@
+# MCU name
+MCU = atmega32u4
+
+# Bootloader selection
+BOOTLOADER = atmel-dfu
+
+# 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 = no         # Console for debug
+COMMAND_ENABLE = no         # Commands for debug and configuration
+NKRO_ENABLE = no            # Enable N-Key Rollover
+BACKLIGHT_ENABLE = yes      # Enable keyboard backlight functionality
+RGBLIGHT_ENABLE = yes       # Enable keyboard RGB underglow
+AUDIO_ENABLE = no           # Audio output
+
+LAYOUTS = ortho_6x4