[Keyboard] Support MJ64 REV3 - a 60% RGB Hotswap with arrow (#11785)

Co-authored-by: Ryan <fauxpark@gmail.com>
Co-authored-by: James Young <18669334+noroadsleft@users.noreply.github.com>
Co-authored-by: Drashna Jaelre <drashna@live.com>

keyboards/melgeek/mj64/rev3/config.h

@@ -0,0 +1,39 @@
+/* Copyright 2020 MelGeek <melgeek001365@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/>.
+ */
+
+#pragma once
+
+/*
+ * Keyboard Matrix Assignments
+ *
+ * Change this to how you wired your keyboard
+ * COLS: AVR pins used for columns, left to right
+ * ROWS: AVR pins used for rows, top to bottom
+ * DIODE_DIRECTION: COL2ROW = COL = Anode (+), ROW = Cathode (-, marked on diode)
+ *                  ROW2COL = ROW = Anode (+), COL = Cathode (-, marked on diode)
+ *
+ */
+
+#define MATRIX_ROW_PINS { B12, B11, B10, B1, A3 }
+#define MATRIX_COL_PINS { B15, A8, B13, A15, B3, B4, B5, B8, B9, C13, C14, C15, A0, A1 }
+#define UNUSED_PINS
+
+/* COL2ROW, ROW2COL*/
+#define DIODE_DIRECTION COL2ROW
+
+#define DRIVER_1_LED_TOTAL 72
+#define DRIVER_LED_TOTAL DRIVER_1_LED_TOTAL
+#define DRIVER_INDICATOR_LED_TOTAL 0