Needs an update with new WABT

SIMD opcodes have been renumbered in the spec - see https://github.com/WebAssembly/simd/issues/129 - and updated in WABT.

We need to regenerate JS with a newest WABT and publish a new version.

I've tried to make a PR, but it only changed README because `dist` is not part of the repo, so it's probably best that this change is done by whoever has publish access.