added keyboard device demo

demos/device/keyboard/main.c

@@ -0,0 +1,25 @@
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+
+#include <cr_section_macros.h>
+#include <NXP/crp.h>
+#include "tusb.h"
+
+// Variable to store CRP value in. Will be placed automatically
+// by the linker when "Enable Code Read Protect" selected.
+// See crp.h header for more information
+__CRP const unsigned int CRP_WORD = CRP_NO_CRP ;
+
+int main(void) 
+{
+  SystemInit();
+  tusb_init();
+
+  while (1)
+  {
+
+  }
+
+  return 0;
+}