Convert BigRedButton ctor into just a Bundle

The BigRedButton isn't doing anything that requires the `Commands`, so
it'll be turned back into just a Bundle.

src/widgets/mod.rs

@@ -91,9 +91,12 @@ fn machine_ui_base(commands: &mut Commands, header: impl Into<String>, theme: &U
 pub struct BigRedButton;
 
 impl BigRedButton {
-  // TODO: Hook up action handling (callback? Observer? Some other weird component?)
+  /// Default bundle for a Big Red Button. Remember to attach on-press observers!
-  fn spawn_big_red_button(commands: &mut ChildSpawnerCommands, text: impl Into<String>) {
+  ///
-    let mut builder = commands.spawn((
+  /// I haven't figure out what will receive the on-press events, so I'm moving
+  /// the problem. It will not be the button's job to hook up the event notice.
+  fn bundle(text: impl Into<String>) -> impl Bundle {
+    (
       Button,
       BigRedButton,
       Node {
@@ -117,7 +120,7 @@ impl BigRedButton {
         TextColor(WHITE.into()),
         TextShadow::default(),
       ],
-    ));
+    );
   }
 
   /// Re-color the button when a pointer passes over it