Indent code in speaker notes (#476)

* Indent code in speaker notes

#475

* Update stack.md

* Update destructuring-arrays.md

* Update hashmap.md

* Update traits.md

src/pattern-matching/destructuring-arrays.md

@@ -12,22 +12,22 @@ You can destructure arrays, tuples, and slices by matching on their elements:
 * Destructuring of slices of unknown length also works with patterns of fixed length.
 
 
-```rust,editable
-fn main() {
-    inspect(&[0, -2, 3]);
-    inspect(&[0, -2, 3, 4]);
-}
+     ```rust,editable
+     fn main() {
+         inspect(&[0, -2, 3]);
+         inspect(&[0, -2, 3, 4]);
+     }
 
-#[rustfmt::skip]
-fn inspect(slice: &[i32]) {
-    println!("Tell me about {slice:?}");
-    match slice {
-        &[0, y, z] => println!("First is 0, y = {y}, and z = {z}"),
-        &[1, ..]   => println!("First is 1 and the rest were ignored"),
-        _          => println!("All elements were ignored"),
-    }
-}
-```
+     #[rustfmt::skip]
+     fn inspect(slice: &[i32]) {
+         println!("Tell me about {slice:?}");
+         match slice {
+             &[0, y, z] => println!("First is 0, y = {y}, and z = {z}"),
+             &[1, ..]   => println!("First is 1 and the rest were ignored"),
+             _          => println!("All elements were ignored"),
+         }
+     }
+     ```
   
 * Create a new pattern using `_` to represent an element. 
 * Add more values to the array.