add comment for arc()

src/lib.rs

@@ -20,6 +20,8 @@ pub fn start() {
 
   context.begin_path();
 
+// arc(x, y, radius, startAngle, endAngle, counterclockwise)
+// Draws an arc which is centered at (x, y) position with radius r starting at startAngle and ending at endAngle going in the given direction indicated by counterclockwise (defaulting to clockwise).
   context
     .arc(75.0, 75.0, 50.0, 0.0, f64::consts::PI * 2.0)
     .unwrap();