Enable 'std' feature on critical-section for WASM

This fixes the WASM support which was failing due to missing
critical-section implementation. This also upgrades the bindgen
dependency and ensures that tooling works.

examples/wasm/README.md

@@ -3,7 +3,7 @@
 Examples use a CLI tool named `wasm-pack` to build this example:
 
 ```
-cargo install wasm-pack
+cargo install wasm-pack --version 0.9.1
 ```
 
 ## Building