add some comments and add latest version of the kernel

examples/wasmtime/src/preview1.rs

@@ -1,4 +1,8 @@
 #![allow(dead_code)]
+///! This file provide the interface of WASI preview1 to HermitOS
+///!
+///! NOTE: The current version assumes that / is the current
+///! working directory of the WASI application.
 use std::cmp::Ordering;
 use std::mem::MaybeUninit;
 use std::sync::{Mutex, OnceLock};