Corrected typing description in doc

Author: Ajacmac

src/libserialize/json.rs

@@ -365,7 +365,7 @@ impl std::error::Error for EncoderError {
 }
 
 impl From<fmt::Error> for EncoderError {
-    /// Converts a `fmt::Error` into `EncoderError`
+    /// Converts a [`fmt::Error`] into `EncoderError`
     ///
     /// This conversion does not allocate memory.
     fn from(err: fmt::Error) -> EncoderError { EncoderError::FmtError(err) }