add digitalWrite functions

examples/nightrider.rs

@@ -0,0 +1,21 @@
+use std::{thread::sleep, time::Duration};
+
+use b15f::b15f::B15F;
+
+fn main() {
+	let mut drv = B15F::new().unwrap();
+
+	let mut position = 0;
+	let mut direction = 1;
+
+	loop {
+		drv.digital_write::<0>(1 << position);
+
+		position += direction;
+		if position >= 7 || position <= 0 {
+			direction *= -1;
+		}
+
+		sleep(Duration::from_millis(50));
+	}
+}