Update wasm-example's README.md

crates/wasm-example/README.md

@@ -5,11 +5,15 @@ An example of model code which can be compiled to WASM and executed in the viewe
 Use [cargo watch](https://crates.io/crates/cargo-watch) to listen for file changes and rebuild the model file whenever code is edited:
 
 ```
+# From the project root
 $ cargo watch -x "build -p wasm-example --release --target wasm32-unknown-unknown"
 ```
 
 Run the viewer app with:
 
 ```
-$ cargo run --release --no-default-features --bin viewer
+# From the project root, while the "cargo watch" command above is running.
+$ cargo run --release --bin viewer -- --wasm-path target/wasm32-unknown-unknown/release/wasm_example.wasm
 ```
+
+Edit `src/lib.rs` and save to see the model code get recompiled, and see the model in the viewer app get updated.