extend_low_i32x4_u: Wasm SIMD conversion instruction

(module
  (import "console" "log" (func $log (param i64)))
  (func $main
    v128.const i32x4 2090 2091 2092 2093

    i64x2.extend_low_i32x4_u
    i64x2.extract_lane 0
    call $log ;; log the result
  )
  (start $main)
)

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