[Keyboard] add ein_60 (#14398)

Co-authored-by: Drashna Jaelre <drashna@live.com>
Co-authored-by: Ryan <fauxpark@gmail.com>

keyboards/ein_60/rules.mk

@@ -0,0 +1,26 @@
+# MCU name
+MCU = at90usb1286
+
+# Bootloader selection
+BOOTLOADER = qmk-dfu
+
+# 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 = yes        # Console for debug
+COMMAND_ENABLE = yes        # 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 = no        # Enable keyboard RGB underglow
+AUDIO_ENABLE = no           # Audio output
+RGB_MATRIX_ENABLE = no      # Enable for pretty RGB matrix effects
+RGB_MATRIX_DRIVER = WS2812  # Define RGB Matrix
+ENCODER_ENABLE = yes        # Enables the use of one or more encoders
+OLED_ENABLE = yes           # Enables the use of OLED displays
+OLED_DRIVER = SSD1306