Add MxSS keyboard (#3335)

* Added basic MxSS support

* Fixed split RSHFT for ISO layouts

* Updated readme.md for MxSS

* Added initial support for individual control of front RGB LEDs

* Changed RGBLED color selection to work using hue and saturation rather than RGB
Added code for LED state change on layer change

* Avoid needing an entire 8 bits to store the brightness value

* Added custom keycodes, along with their handlers

* Added EEPROM storage for front LED config

* Fixed up ability to use QMK Configurator and updated readme.md

* Applied suggested changes from pull request: https://github.com/standard/standard/issues/452

Updated name in license descriptions
Updated layouts to snake case
Corrected mistakes in info.json
Updated layer_colors to a weak attributed array in mxss.c

* Defined a new safe range for custom keycodes in keymap.c

keyboards/mxss/templates/keymap.c

@@ -0,0 +1,42 @@
+/* Copyright 2018 REPLACE_WITH_YOUR_NAME
+ *
+ * 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
+#include "mxss_frontled.h"
+
+// Helpful defines
+#define _______ KC_TRNS
+
+// Predefined colors for layers
+// Format: {hue, saturation}
+// {0, 0} to turn off the LED
+// Add additional rows to handle more layers
+hs_set layer_colors[] = {
+    [0] = {0,     0},  // Color for Layer 0
+    [1] = {86,    255},  // Color for Layer 1
+    [2] = {36,    255},  // Color for Layer 2
+    [3] = {185,   255},  // Color for Layer 3
+};
+const size_t lc_size = sizeof(layer_colors) / sizeof(uint16_t);
+
+// Use NEW_SAFE_RANGE to define new custom keycodes in order to not overwrite the ones used for front LED control
+enum custom_keycodes {
+  MY_KEYCODE = NEW_SAFE_RANGE, 
+};
+
+
+const uint16_t PROGMEM keymaps[][MATRIX_ROWS][MATRIX_COLS] = {
+__KEYMAP_GOES_HERE__
+};