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/led.h

@@ -0,0 +1,43 @@
+/*
+Copyright 2011 Jun Wako <wakojun@gmail.com>
+
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 2 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+Ported to QMK by Peter Roe <pete@13bit.me>
+*/
+
+#ifndef LED_H
+#define LED_H
+#include "stdint.h"
+
+
+/* keyboard LEDs */
+#define USB_LED_NUM_LOCK                0
+#define USB_LED_CAPS_LOCK               1
+#define USB_LED_SCROLL_LOCK             2
+#define USB_LED_COMPOSE                 3
+#define USB_LED_KANA                    4
+
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+void led_set(uint8_t usb_led);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif