Rust can't find 'crate' for 'std'
You need to add the wasm32-unknown-unknown target for the nightly toolchain if that's what you are using:
rustup target add --toolchain nightly wasm32-unknown-unknown
You need to add the wasm32-unknown-unknown target for the nightly toolchain if that's what you are using:
rustup target add --toolchain nightly wasm32-unknown-unknown