add criterion benchmark

benches/large_grid.rs

@@ -0,0 +1,17 @@
+use criterion::{black_box, criterion_group, criterion_main, Criterion};
+use gol_bitwise::region::Region;
+
+fn large_grid(c: &mut Criterion) {
+	const SIZE: usize = 2048 / gol_bitwise::tile::WIDTH; // same number of cells regardless of tile size
+	let mut region = black_box(Region::new(SIZE, SIZE));
+	region.randomise();
+
+	c.bench_function("large grid", |b| {
+		b.iter(|| {
+			region.step();
+		})
+	});
+}
+
+criterion_group!(benches, large_grid);
+criterion_main!(benches);