feat: add rust demo

examples/tos_meets_rust/app/src/lib.rs

@@ -0,0 +1,23 @@
+#![no_std]
+
+extern crate cortex_m;
+
+mod bridge;
+
+use crate::bridge::*;
+use cty::*;
+
+#[no_mangle]
+pub extern "C" fn application_entry_rust() -> c_void {
+    unsafe {
+        rust_print(b"[+] Welcome to the RUST-WORLD in TencentOS :)".as_ptr());
+        rust_mqtt_daemon();
+    }
+
+    loop {
+        unsafe {
+            rust_print(b"[+] This is a mqtt demo!".as_ptr());
+            rust_sleep(5000u32);
+        }
+    }
+}