added hello-world wasm example and npmPackage nix derivation

src/platform/wasm/mod.rs

@@ -0,0 +1,19 @@
+mod utils;
+
+use wasm_bindgen::prelude::*;
+
+// When the `wee_alloc` feature is enabled, use `wee_alloc` as the global
+// allocator.
+#[cfg(feature = "wee_alloc")]
+#[global_allocator]
+static ALLOC: wee_alloc::WeeAlloc = wee_alloc::WeeAlloc::INIT;
+
+#[wasm_bindgen]
+extern {
+    fn alert(s: &str);
+}
+
+#[wasm_bindgen]
+pub fn greet() {
+    alert("Hello, wasm-game-of-life!");
+}