feat(example): added sound system example

examples/hello_sound.rs

@@ -0,0 +1,23 @@
+use comet::prelude::*;
+
+fn setup(app: &mut App, _renderer: &mut Renderer2D) {
+    app.load_audio("startup", "res/sounds/hit.ogg");
+    app.play_audio("startup", true); // second parameter loops the sound
+
+    // here the float indicated the volume percentage
+    // in the standard backend for audio in comet (kira) 0.0 is equal to -20dB and 1.0 to 0dB
+    app.set_volume("startup", 1.0);
+}
+
+#[allow(unused_variables)]
+fn update(app: &mut App, renderer: &mut Renderer2D, dt: f32) {
+    // in this example, update_audio doesnt do anything because the kira audio system
+    // doesnt need any update
+    app.update_audio(dt);
+}
+
+fn main() {
+    App::new()
+        .with_title("Comet Audio Example")
+        .run::<Renderer2D>(setup, update);
+}