implement Deref for State<S> (#8668)

# Objective

- Allow for directly call methods on states without first calling
`state.get().my_method()`

## Solution

- Implement `Deref` for `State<S>` with `Target = S`
---
*I did not implement `DerefMut` because states hold no data and should
only be changed via `NextState::set()`*

crates/bevy_ecs/src/schedule/state.rs

@@ -1,6 +1,7 @@
 use std::fmt::Debug;
 use std::hash::Hash;
 use std::mem;
+use std::ops::Deref;
 
 use crate as bevy_ecs;
 use crate::change_detection::DetectChangesMut;
@@ -95,6 +96,14 @@ impl<S: States> PartialEq<S> for State<S> {
     }
 }
 
+impl<S: States> Deref for State<S> {
+    type Target = S;
+
+    fn deref(&self) -> &Self::Target {
+        self.get()
+    }
+}
+
 /// The next state of [`State<S>`].
 ///
 /// To queue a transition, just set the contained value to `Some(next_state)`.