[Keyboard] Add avalanche (#16407)

* [Keyboard] Add avalanche

* PR feedback

* Update keyboards/avalanche/v1/config.h

* Update keyboards/avalanche/v1/v1.h

* Update keyboards/avalanche/v2/config.h

* Update keyboards/avalanche/v2/v2.h

* Update keyboards/avalanche/v3/config.h

* Update keyboards/avalanche/v3/v3.h

* Apply suggestions from code review

* Remove rules.mk comment and fix other comments.

* Shared encoder code, follow conventions in rules.mk files.

* Remove config files which do not change defaul behavior.

keyboards/avalanche/v1/rules.mk

@@ -0,0 +1,20 @@
+# 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 = no         # Console for debug
+COMMAND_ENABLE = no         # Commands for debug and configuration
+NKRO_ENABLE = yes           # Enable N-Key Rollover
+BACKLIGHT_ENABLE = no       # Enable keyboard backlight functionality
+RGBLIGHT_ENABLE = no        # Enable keyboard RGB underglow
+AUDIO_ENABLE = no           # Audio output
+
+SPLIT_KEYBOARD = yes