Add extending WASI plugin example

examples/plugin-for-example/src/bin.rs

@@ -0,0 +1,14 @@
+extern "C" {
+    fn it_works() -> i32;
+}
+
+#[no_mangle]
+pub fn plugin_entrypoint(n: i32) -> i32 {
+    println!("It works from inside WASI");
+    let result = unsafe { it_works() };
+    result + n
+}
+
+pub fn main() {
+    println!("hello");
+}

examples/plugin-for-example/src/main.rs

@@ -0,0 +1,12 @@
+extern "C" {
+    fn it_works() -> i32;
+}
+
+#[no_mangle]
+pub fn plugin_entrypoint(n: i32) -> i32 {
+    println!("Hello from inside WASI");
+    let result = unsafe { it_works() };
+    result + n
+}
+
+pub fn main() {}