wasm command

wasm is a simple example that loads and executes a wasm file function. greet.wasm, Cargo.toml and greet.rs were copied from the example provided by the wazero library: https://github.com/tetratelabs/wazero/blob/v1.0.0-pre.3/examples/allocation/rust/greet.go

New Concepts: 1. Load a wasm file compiled from: cargo build --release --target wasm32-unknown-unknown 2. Execute a wasm function within a DoFn