make the timer trigger (#935)

Co-authored-by: Tony <[email protected]>

Author: rmsthebest

examples/2d/sprite_sheet.rs

@@ -9,10 +9,12 @@ fn main() {
 }
 
 fn animate_sprite_system(
+    time: Res<Time>,
     texture_atlases: Res<Assets<TextureAtlas>>,
     mut query: Query<(&mut Timer, &mut TextureAtlasSprite, &Handle<TextureAtlas>)>,
 ) {
-    for (timer, mut sprite, texture_atlas_handle) in query.iter_mut() {
+    for (mut timer, mut sprite, texture_atlas_handle) in query.iter_mut() {
+        timer.tick(time.delta_seconds);
         if timer.finished() {
             let texture_atlas = texture_atlases.get(texture_atlas_handle).unwrap();
             sprite.index = ((sprite.index as usize + 1) % texture_atlas.textures.len()) as u32;