extend_low_i8x16_s: Wasm SIMD conversion instruction

(module
  (import "console" "log" (func $log (param i32)))
  (func $main
    v128.const i8x16 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32

    i16x8.extend_low_i8x16_s
    i16x8.extract_lane_s 0
    call $log ;; log the result
  )
  (start $main)
)

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