feat: add Synthwave Racer visualizer with custom WGSL shader

Author: Soddentrough

src/engine.rs

@@ -665,6 +665,7 @@ impl<'a> VulkanEngine<'a> {
                 13 => include_str!("shaders/vis_starfield.wgsl"),
                 14 => include_str!("shaders/vis_rain.wgsl"),
                 15 => include_str!("shaders/vis_3drain.wgsl"),
+                16 => include_str!("shaders/vis_synthwaveracer.wgsl"),
                 _ => include_str!("shaders/vis_spectrum.wgsl"),
             }
         };