feat(shields) Add Redox Shield Support (#1002)

* Add redox shield support

* typo

* Pull request fixes

* requested changes

add underglow, add copyright, remove display

* remove because of no display

* comment fix

* bt clear

app/boards/shields/redox/Kconfig.defconfig

@@ -0,0 +1,18 @@
+# Copyright (c) 2021 The ZMK Contributors
+# SPDX-License-Identifier: MIT
+if SHIELD_REDOX_LEFT
+
+config ZMK_KEYBOARD_NAME
+	default "Redox"
+
+config ZMK_SPLIT_BLE_ROLE_CENTRAL
+	default y
+
+endif
+
+if SHIELD_REDOX_LEFT || SHIELD_REDOX_RIGHT
+
+config ZMK_SPLIT
+	default y
+
+endif