selection: Create it's dedicated class

includes/snapping.hpp

@@ -0,0 +1,24 @@
+/*
+* File name: selection.cpp
+* Author: lejulien
+* Date created: 01-01-1970 00:59:59
+// Date modified: 12-01-2026 21:30:10
+* ------
+*/
+
+#pragma once
+
+#include <types.hpp>
+
+#include <raylib.h>
+#include <cmath>
+
+Vector2 snapToGrid(Vector2 screen, int cell_size) {
+  return {static_cast<float>(round(screen.x / cell_size) * cell_size),
+          static_cast<float>(round(screen.y / cell_size) * cell_size)};
+}
+
+Vector2i screenToGrid(Vector2 screen, int cell_size) {
+  return {static_cast<int>(round(screen.x / cell_size)),
+          static_cast<int>(round(screen.y / cell_size))};
+}