Move Zephyr app into subdirectory.

app/include/zmk/keys.h

@@ -0,0 +1,17 @@
+#pragma once
+
+#include <zephyr.h>
+#include <dt-bindings/zmk/keys.h>
+
+typedef u32_t zmk_key;
+typedef u8_t zmk_action;
+typedef u8_t zmk_mod;
+typedef u8_t zmk_mod_flags;
+
+struct zmk_key_event
+{
+    u32_t column;
+    u32_t row;
+    zmk_key key;
+    bool pressed;
+};