[Keyboard] Added xealousbrown keyboard (#4945)

* Added xealousbrown keyboard.

* Changed to pragma once in config.h

* Update keyboards/handwired/xealousbrown/rules.mk

Added bootloader.

Co-Authored-By: alex-ong <the.onga@gmail.com>

* Update keyboards/handwired/xealousbrown/config.h

Commented out IS_COMMAND() since it is already default value.

Co-Authored-By: alex-ong <the.onga@gmail.com>

keyboards/handwired/xealousbrown/xealousbrown.c

@@ -0,0 +1,8 @@
+#include "xealousbrown.h"
+
+void matrix_init_kb(void) {
+	// put your keyboard start-up code here
+	// runs once when the firmware starts up
+
+	matrix_init_user();
+}