Add configuration option for default grid size.

src/conf.zig

@@ -26,6 +26,11 @@ pub const mouse_right_btn: c_int = 1;
 // * true: click to enter, draw, release to exit.
 pub const mouse_graphic_tablet: bool = false;
 
+pub const default_grid_size = .{
+    .width = 16,
+    .height = 16,
+};
+
 pub const theme = .{
     .background = ray.BLACK,
     .mode = .{

src/main.zig

@@ -49,7 +49,8 @@ pub fn main() void {
 
     // Try to load level, is doesn't exist create it.
     var level: Level = Level.init_read(allocator, level_path) catch create: {
-        break :create Level.init(allocator, 16, 16) catch unreachable;
+        break :create Level.init(allocator, conf.default_grid_size.width, conf.default_grid_size.height) catch
+            unreachable;
     };
     defer level.deinit(allocator);