[Keyboard] Add Keybage folder for RadPad (#9745)

* [Keyboard] Initial Keybage/RadPad firmware

* [Keyboard] RadPad apply pull request feedback

- Change `LAYOUT_***_Encoders` to `LAYOUT_***_encoders` in <keyboard>.h
- Remove bootloader comments and unnecessary build options from rules.mk
- Use `LTO_ENABLE`
- Remove empty config.h from default keymap
- Remove trailing ` \` from keymap

* [Keyboard] RadPad fix info.json

- Change `LAYOUT_***_Encoders` to `LAYOUT_***_encoders` in info.json

* [Keyboard] Add host LED status to OLED display

* [Keyboard] Use LAYOUT_4x4_encoders, not LAYOUT

* [Keyboard] Use LAYOUT_4x4_encoders, not LAYOUT

* [Keyboard] Remove DESCRIPTION from config.h

keyboards/keybage/radpad/rules.mk

@@ -0,0 +1,25 @@
+# MCU name
+MCU = atmega32u4
+
+# Bootloader selection
+BOOTLOADER = caterina
+
+# Build Options
+#   change yes to no to disable
+#
+BOOTMAGIC_ENABLE = lite     # Virtual DIP switch configuration
+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
+# Do not enable SLEEP_LED_ENABLE. it uses the same timer as BACKLIGHT_ENABLE
+SLEEP_LED_ENABLE = no       # Breathing sleep LED during USB suspend
+# if this doesn't work, see here: https://github.com/tmk/tmk_keyboard/wiki/FAQ#nkro-doesnt-work
+NKRO_ENABLE = no            # USB Nkey Rollover
+BACKLIGHT_ENABLE = no       # Enable keyboard backlight functionality
+RGBLIGHT_ENABLE = yes       # Enable keyboard RGB underglow
+BLUETOOTH_ENABLE = no       # Enable Bluetooth
+AUDIO_ENABLE = no           # Audio output
+ENCODER_ENABLE = yes
+OLED_DRIVER_ENABLE = yes
+LTO_ENABLE = yes