improve layer switching

layer.h

@@ -0,0 +1,13 @@
+#ifndef LAYER_H
+#define LAYER_H 1
+
+#include <stdint.h>
+
+
+/* return keycode for switch */
+uint8_t layer_get_keycode(uint8_t row, uint8_t col);
+
+/* process layer switching */
+void layer_switching(uint8_t fn_bits);
+
+#endif