extend_low_i16x8_s: Wasm SIMD conversion instruction

(module
  (import "console" "log" (func $log (param i32)))
  (func $main
    v128.const i16x8 200 210 220 230 240 250 260 270

    i32x4.extend_low_i16x8_s
    i32x4.extract_lane 0
    call $log ;; log the result
  )
  (start $main)
)

WebAssembly.instantiateStreaming(fetch("{%wasm-url%}"), { console });