derive Default for State in observables e.g.

nexosim-util/examples/observables.rs

@@ -48,18 +48,14 @@ pub enum ModeId {
 }
 
 /// Processor state.
+#[derive(Default)]
 pub enum State {
+    #[default]
     Off,
     Idle,
     Processing(AutoActionKey),
 }
 
-impl Default for State {
-    fn default() -> Self {
-        State::Off
-    }
-}
-
 impl Observable<ModeId> for State {
     fn observe(&self) -> ModeId {
         match *self {