Implement raise/lower for default keymap.

* Properly allow includes for keymaps to allow defining
  custom keycodes, and then adding them to the
  keymap.overlay file.
* Fix keymap.c loading after build refactor.
* Fix for deactivating a layer working properly.
* Fix default keymap to put transparent in proper spots to
  make raise/lower keycodes work as expected.
* Add custom raise/lower keycode handling to default
  keymap.

boards/shields/petejohanson_handwire/keymaps/default/keymap.c

@@ -1,7 +1,34 @@
 
 #include <zmk/keys.h>
+#include <zmk/keymap.h>
+#include <keymap.h>
 
 bool zmk_handle_key_user(struct zmk_key_event *key_event)
 {
+	switch (key_event->key)
+	{
+	case CC_LOWR:
+		if (key_event->pressed)
+		{
+			zmk_keymap_layer_activate(1);
+		}
+		else
+		{
+			zmk_keymap_layer_deactivate(1);
+		}
+
+		return false;
+	case CC_RAIS:
+		if (key_event->pressed)
+		{
+			zmk_keymap_layer_activate(2);
+		}
+		else
+		{
+			zmk_keymap_layer_deactivate(2);
+		}
+		return false;
+	}
+
 	return true;
 };