add wasm

wasm/src/lib.rs

@@ -0,0 +1,13 @@
+extern crate wasm_bindgen;
+
+use wasm_bindgen::prelude::*;
+
+#[wasm_bindgen]
+extern {
+    pub fn alert(s: &str);
+}
+
+#[wasm_bindgen]
+pub fn greet(name: &str) {
+    alert(&format!("Hello, {}!", name));
+}