After installing rust and cargo via rustup, add the wasm target and then compile the module:

rustup target add wasm32-unknown-emscripten
cargo install wasm-bindgen-cli
cargo build --target wasm32-unknown-emscripten
wasm-bindgen target/wasm32-unknown-emscripten/debug/bindgenhello.wasm --out-dir target/wasm32-unknown-emscripten/debug

Then try bundling with npm run bundle