Merge #147

147: Adding the new flag required for the wasm build check r=curquiza a=sanders41

The wasm build now requires the `--features=sync` flag as mentioned here #132 (comment). Without this flag the build fails so I added it to the instructions in the `CONTRIBUTING.md`.

Co-authored-by: Paul Sanders <[email protected]>

Author: bors[bot]

CONTRIBUTING.md

@@ -45,7 +45,7 @@ Also, the WASM example compilation should be checked:
 
 ```bash
 rustup target add wasm32-unknown-unknown
-cargo check --example web_app --target wasm32-unknown-unknown
+cargo check --example web_app --target wasm32-unknown-unknown --features=sync
 ```
 
 Each PR should pass the tests to be accepted.