Correction de l'include

practical_work/planets/skeleton/main.c

 #include "gfx/gfx.h"
 #include "vec2/vec2.h"
-#include "planet/planet.h"
+#include "celestial_body/celestial_body.h"
 #include <stdio.h>
 #include <stdlib.h>
 #include <time.h>