Fix sample code

README.md

@@ -237,20 +237,21 @@ If you need support for conversions from these values, you should use `TryFromPr
 
   - This means, for instance, that the following is UB:
 
-    ```rust ,no_run
+    ```rust,no_run
     use num_enum::UnsafeFromPrimitive;
 
     #[derive(UnsafeFromPrimitive)]
     #[repr(u8)]
     enum Number {
         Zero = 0,
 
-        // same for `#[num_enum(catch_all)]`, and `#[num_enum(alternatives = [2, ...])]`
-        #[default]        
+        // Same for `#[num_enum(catch_all)]`, and `#[num_enum(alternatives = [2, ...])]`
+        #[num_enum(default)]
         One = 1,
     }
     let _undefined_behavior = unsafe { Number::unchecked_transmute_from(2) };
     ```
+
 ```rust
 use num_enum::UnsafeFromPrimitive;