Try fixing the moving rainbow red purple glitch

src/pattern/moving_rainbow.rs

@@ -41,6 +41,8 @@ impl Pattern for MovingRainbow {
         // RAINBOW.len() * width
         let length_factor = u16::try_from(RAINBOW.len())
             .or(Err(()))?
+            .checked_add(self.skip.into())
+            .ok_or(())?
             .saturating_mul(u16::from(self.width));
         // The length of the buffer
         // Always a factor of length_factor