Keyboard: Ported ADB-to-USB converter from TMK to QMK (#3931)

* Ported ADB-to-USB converter from TMK to QMK

* Updated pull request with reviewer suggestions.

* Removed precompiled header file type (gch) from gitignore per reviewer request

* Update keyboards/converter/adb_usb/matrix.c

Changed instances of matrix_init_quantum to matrix_scan_quantum.

* Update keyboards/converter/adb_usb/matrix.c

Co-Authored-By: 13-bit <pete@13bit.me>

keyboards/converter/adb_usb/rules.mk

@@ -0,0 +1,73 @@
+# MCU name
+# atmega32u4 	Teensy2.0
+# atemga32u4	TMK Converter rev.1
+# atemga32u2	TMK Converter rev.2
+MCU = atmega32u4
+
+# Processor frequency.
+#     This will define a symbol, F_CPU, in all source code files equal to the
+#     processor frequency in Hz. You can then use this symbol in your source code to
+#     calculate timings. Do NOT tack on a 'UL' at the end, this will be done
+#     automatically to create a 32-bit value in your source code.
+#
+#     This will be an integer division of F_USB below, as it is sourced by
+#     F_USB after it has run through any CPU prescalers. Note that this value
+#     does not *change* the processor frequency - it should merely be updated to
+#     reflect the processor speed set externally so that the code can use accurate
+#     software delays.
+#
+F_CPU = 16000000
+# F_CPU = 8000000
+
+#
+# LUFA specific
+#
+# Target architecture (see library "Board Types" documentation).
+ARCH = AVR8
+
+# Input clock frequency.
+#     This will define a symbol, F_USB, in all source code files equal to the
+#     input clock frequency (before any prescaling is performed) in Hz. This value may
+#     differ from F_CPU if prescaling is used on the latter, and is required as the
+#     raw input clock is fed directly to the PLL sections of the AVR for high speed
+#     clock generation for the USB and other AVR subsections. Do NOT tack on a 'UL'
+#     at the end, this will be done automatically to create a 32-bit value in your
+#     source code.
+#
+#     If no clock division is performed on the input clock inside the AVR (via the
+#     CPU clock adjust registers or the clock division fuses), this will be equal to F_CPU.
+F_USB = $(F_CPU)
+
+# Interrupt driven control endpoint task(+60)
+OPT_DEFS += -DINTERRUPT_CONTROL_ENDPOINT
+
+# Bootloader
+#     This definition is optional, and if your keyboard supports multiple bootloaders of
+#     different sizes, comment this out, and the correct address will be loaded
+#     automatically (+60). See bootloader.mk for all options.
+BOOTLOADER = caterina
+
+# Boot Section Size in *bytes*
+#   Teensy halfKay   512
+#   Teensy++ halfKay 1024
+#   Atmel DFU loader 4096	for TMK Converter rev.1/rev.2
+#   LUFA bootloader  4096
+#   USBaspLoader     2048
+
+# Build Options
+#   comment out to disable the options.
+#
+BOOTMAGIC_ENABLE	= no			# Virtual DIP switch configuration(+1000)
+MOUSEKEY_ENABLE		= no			# Mouse keys(+4700)
+CONSOLE_ENABLE		= no			# Console for debug(+400)
+COMMAND_ENABLE		= no  		# Commands for debug and configuration
+SLEEP_LED_ENABLE 	= no  		# Breathing sleep LED during USB suspend
+NKRO_ENABLE 		  = no			# USB Nkey Rollover - not yet supported in LUFA
+EXTRAKEY_ENABLE		= yes
+USB_HID_ENABLE 		= yes
+BACKLIGHT_ENABLE 	= no
+#BLUETOOTH 			= AdafruitBLE   # For Adafruit Feather 32U4 BLE support, uncomment this line
+
+CUSTOM_MATRIX = yes
+SRC = matrix.c \
+      adb.c