Update includes to to be relative to src directory

Don't use relative imports like `../foo.h` as those depend on the
relative position of both files. Rather than that use imports relative
to the `src` directory, which explicitly is part of the include
directories.

src/displayapp/screens/Screen.h

@@ -1,7 +1,7 @@
 #pragma once
 
 #include <cstdint>
-#include "../TouchEvents.h"
+#include "displayapp/TouchEvents.h"
 #include <lvgl/lvgl.h>
 
 namespace Pinetime {