Add Example tests and fix raw value extraction for boolean types

Add two godoc Example tests:
- ExampleDecoder_EnableUnmarshalerInterface_dynamicConfig: shows dynamic
  unmarshaling based on a type field
- ExampleDecoder_EnableUnmarshalerInterface_rawMessage: demonstrates
  RawMessage usage for deferred parsing

Fix handleKeyValuesUnmarshaler to handle values where Raw.Length == 0
(like boolean types) by using value.Data as fallback.

unmarshaler.go

@@ -729,8 +729,15 @@ func (d *decoder) handleKeyValuesUnmarshaler(u unstable.Unmarshaler) (reflect.Va
 		// Get the raw value bytes
 		value := expr.Value()
 		if value != nil {
-			raw := d.p.Raw(value.Raw)
-			buf = append(buf, raw...)
+			if value.Raw.Length > 0 {
+				// Use raw bytes from the original document
+				raw := d.p.Raw(value.Raw)
+				buf = append(buf, raw...)
+			} else {
+				// Some value types (like Bool) don't have Raw set,
+				// use Data which contains the value representation
+				buf = append(buf, value.Data...)
+			}
 		}
 		buf = append(buf, '\n')
 	}