Address review comments.

Author: dvc94ch

README.md

@@ -2,6 +2,12 @@
 
 Call rust from any language. Take a look at the example to get you started.
 
+This requires `wasm-multi-value-reverse-polyfill` to be in your path when targeting js:
+
+```sh
+cargo install --git https://github.com/vmx/wasm-multi-value-reverse-polyfill --locked
+```
+
 ## Supported languages
 
 - dart