Adds toast support for user centered error handling

[naomijub]

Adds toasts of type:

• info
• warning
• success
• error

Just need to add:

fn system_with_toast(
   // ...
  mut toasts: EventWriter<ToastMessage>,
) {
  // ...
  toasts.send_event(ToastMessage::new(
     &format!("Despawning {entity:?}"),
     egui_toast::ToastKind::Warning,
  ));
}

[codecov]

Codecov Report

Attention: Patch coverage is 70.68404% with 90 lines in your changes are missing coverage. Please review.

Project coverage is 25.32%. Comparing base (82b8287) to head (6a451c4).
Report is 1 commits behind head on main.

Files	Patch %	Lines
crates/editor_ui/src/menu_toolbars.rs	0.00%	55 Missing ⚠️
crates/editor_core/src/toast.rs	94.34%	13 Missing ⚠️
crates/editor_core/src/load.rs	0.00%	12 Missing ⚠️
crates/editor_ui/src/mouse_check.rs	0.00%	5 Missing ⚠️
crates/editor_ui/src/meshless_visualizer.rs	0.00%	4 Missing ⚠️
crates/editor_ui/src/lib.rs	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #229      +/-   ##
==========================================
+ Coverage   23.52%   25.32%   +1.80%     
==========================================
  Files          55       56       +1     
  Lines        7648     7961     +313     
==========================================
+ Hits         1799     2016     +217     
- Misses       5849     5945      +96     

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