hello-wasm sample not works

I install workerd from [npm](https://www.npmjs.com/package/workerd)

After entering `samples/hello-wasm`, I ran:

```
❯ cargo install worker-build
Updating crates.io index
Downloaded worker-build v0.0.9
...
Installed package `worker-build v0.0.9` (executable `worker-build`)

❯ worker-build --release
Installing wasm-pack...
Updating crates.io index
Downloaded wasm-pack v0.11.1
...
Compiling hello-wasm v0.1.0 (/Users/tli/Downloads/toys/workerd/samples/hello-wasm)
Finished release [optimized] target(s) in 11.26s
[INFO]: ⬇️ Installing wasm-bindgen...
...
[INFO]: 📦 Your wasm pkg is ready to publish at /Users/tli/Downloads/toys/workerd/samples/hello-wasm/build.
Installing esbuild...

shim.mjs 14.2kb

⚡ Done in 11ms
```

And there're `index.wasm` and `shim.mjs`:

```
❯ ls build/worker
index.wasm shim.mjs
```

According to the [README](https://github.com/cloudflare/workerd/tree/main/samples/hello-wasm) file:

```
❯ workerd serve config.capnp
❯ echo $?
0
```

It just exit, the 8080 web server not work, just wonder if anything I'd missed?