Add an example of wasm2asm and wasm-bindgen

This commit adds an example of executing the `wasm2asm` tool to generate asm.js
output instead of WebAssembly. This is often useful when supporting older
browsers, such as IE 11, that doesn't have native support for WebAssembly.

examples/asm.js/build.sh

@@ -0,0 +1,25 @@
+#!/bin/sh
+
+set -ex
+
+# Compile our wasm module
+cargo +nightly build --target wasm32-unknown-unknown --release
+
+# Run wasm-bindgen, and note that the `--no-demangle` argument is here is
+# important for compatibility with wasm2asm!
+cargo +nightly run --manifest-path ../../crates/cli/Cargo.toml \
+  --bin wasm-bindgen -- \
+  --no-demangle \
+  ../../target/wasm32-unknown-unknown/release/asmjs.wasm --out-dir .
+
+# Run the `wasm2es6js` primarily with the `--wasm2asm` flag, which will
+# internally execute `wasm2asm` as necessary
+cargo +nightly run --manifest-path ../../crates/cli/Cargo.toml \
+  --bin wasm2es6js -- \
+  asmjs_bg.wasm --wasm2asm -o asmjs_bg.js
+
+# Move our original wasm out of the way to avoid cofusing Webpack.
+mv asmjs_bg.wasm asmjs_bg.bak.wasm
+
+npm install
+npm run serve