Make less use of linked files and folders for better long-term maintainability by moving the source files under the newly created src directory and only linking that directory to the workspace.

right/src/layer.h

@@ -0,0 +1,13 @@
+#ifndef __LAYER_H__
+#define __LAYER_H__
+
+// Macros:
+
+    #define LAYER_ID_BASE  0
+    #define LAYER_ID_MOD   1
+    #define LAYER_ID_FN    2
+    #define LAYER_ID_MOUSE 3
+
+    #define LAYER_COUNT 4
+
+#endif