grid: add a guide grid

src/grid.cpp

@@ -0,0 +1,27 @@
+/*
+* File name: grid.cpp
+* Author: lejulien
+* Date created: 01-01-1970 00:59:59
+// Date modified: 12-01-2026 21:30:10
+* ------
+*/
+
+#include <raylib.h>
+
+#include <grid.hpp>
+
+namespace gol {
+
+Grid::Grid(std::shared_ptr<ctx> context) : context_(context) {}
+
+void Grid::display() {
+  auto cell_size = context_->settings_menu->getCellSize();
+  for (int j = 0; j < context_->world->getHeight(); j++) {
+    for (int i = 0; i < context_->world->getWidth(); i++) {
+      DrawRectangleLines(i * cell_size, j * cell_size, cell_size, cell_size,
+                         GRAY);
+    }
+  }
+}
+
+}  // namespace gol