Make Fuel a required component on machines

It will be pulled in automatically by Bevy, now. I've also set a default
fuel level of 5 units.

src/game/mod.rs

@@ -16,16 +16,22 @@ pub mod machines {
 
   use bevy::prelude::*;
 
+  use crate::game::consumables::Fuel;
+
   #[derive(Component)]
+  #[require(Fuel)]
   pub struct CuttingMachine;
 
   #[derive(Component)]
+  #[require(Fuel)]
   pub struct RotatingMachine;
 
   #[derive(Component)]
+  #[require(Fuel)]
   pub struct FlippingMachine;
 
   #[derive(Component)]
+  #[require(Fuel)]
   pub struct TransposingMachine;
 }
 
@@ -35,6 +41,11 @@ pub mod consumables {
   #[derive(Component)]
   pub struct Fuel(pub u32);
 
+  impl Default for Fuel {
+    fn default() -> Self {
+        Self(5)
+    }
+  }
   #[derive(Event)]
   pub struct FuelChanged;
 }

src/main.rs

@@ -3,7 +3,6 @@ use bevy_inspector_egui::{bevy_egui::EguiPlugin, quick::WorldInspectorPlugin};
 
 use crate::{
   game::{
-    consumables::Fuel,
     machines::{CuttingMachine, FlippingMachine, RotatingMachine, TransposingMachine},
   },
   resources::UiTheme,
@@ -50,7 +49,6 @@ fn dummy_machines(mut commands: Commands) {
   commands
     .spawn((
       CuttingMachine,
-      Fuel(10),
       Sprite::from_color(RED, Vec2::splat(40.0)),
       Transform::from_translation(Vec3::new(-40.0, 40.0, 0.0)),
       Pickable::default(),