[ISSUE #25]Add Debug for CheetahString (#26)

* [ISSUE #25]Add Debug for CheetahString

* fix code style

Author: mxsm

src/cheetah_string.rs

@@ -1,3 +1,4 @@
+use core::fmt;
 use std::cmp::Ordering;
 use std::fmt::Display;
 use std::hash::Hash;
@@ -253,6 +254,12 @@ impl Display for CheetahString {
     }
 }
 
+impl std::fmt::Debug for CheetahString {
+    fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
+        fmt::Debug::fmt(self.as_str(), f)
+    }
+}
+
 /// The `InnerString` enum represents different types of string storage.
 ///
 /// Variants: