core: Rename `PlayerEvent::MouseLeft` to `MouseLeave`

So it's not consfusing with `KeyCode::MouseLeft`.

core/src/events.rs

@@ -22,7 +22,7 @@ pub enum PlayerEvent {
         x: f64,
         y: f64,
     },
-    MouseLeft,
+    MouseLeave,
     MouseWheel {
         delta: MouseWheelDelta,
     },

desktop/src/main.rs

@@ -485,7 +485,7 @@ impl App {
                             }
                             WindowEvent::CursorLeft { .. } => {
                                 let mut player_lock = player.lock().unwrap();
-                                player_lock.handle_event(PlayerEvent::MouseLeft);
+                                player_lock.handle_event(PlayerEvent::MouseLeave);
                                 if player_lock.needs_render() {
                                     window.request_redraw();
                                 }