[Keyboard] Add MachKeyboards Mach3 (#14791)

Co-authored-by: Ryan <fauxpark@gmail.com>

keyboards/machkeyboards/mach3/keymaps/via/keymap.c

@@ -0,0 +1,24 @@
+/* Copyright 2021 Mach Keyboards
+ *
+ * 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/>.
+ */
+#include QMK_KEYBOARD_H
+
+const uint16_t PROGMEM keymaps[][MATRIX_ROWS][MATRIX_COLS] = {
+  [0] = LAYOUT_3x3(
+    BL_INC,    BL_DEC,    BL_BRTG,
+    BL_INC,    BL_DEC,    BL_BRTG,
+    BL_INC,    BL_DEC,    BL_BRTG
+  )
+};

keyboards/machkeyboards/mach3/keymaps/via/rules.mk

@@ -0,0 +1,2 @@
+VIA_ENABLE = yes
+LTO_ENABLE = yes