feat: Fix the sync.rs doc example

Author: uttarayan21

src/sync.rs

@@ -2,6 +2,8 @@
 //! This api allows use of mnn in a thread-safe manner
 //! # Example
 //! ```rust,no_run
+//! use mnn::sync::*;
+//! use mnn::*;
 //! let interpreter = Interpreter::from_bytes([0; 100]).expect("Failed to create interpreter");
 //! let config = ScheduleConfig::new();
 //! let session_handle = SessionHandle::new(interpreter, config).expect("Failed to create session handle");