add hhkb bluetooth functionality (rn42) (#2693)

* add hhkb bluetooth functionality (rn42)

pretty much straight from tmk

some minor changes to make things work

* hhkb jp personal keymap

* Revert "hhkb jp personal keymap"

This reverts commit 886713d8bb98572f03110f285706a8140a083892.

keyboards/hhkb/rn42/rn42_task.h

@@ -0,0 +1,14 @@
+#ifndef RN42_TASK_H
+#define RN42_TASK_H
+
+#include <stdbool.h>
+#include "rn42.h"
+
+#ifdef NKRO_ENABLE
+bool rn42_nkro_last;
+#endif
+
+void rn42_task_init(void);
+void rn42_task(void);
+
+#endif