Fix extract_lane instructions in README

[chharvey]

The i32x4 and i64x2 only have extract_lane (there is no signed or unsigned version).

See https://webassembly.github.io/spec/core/syntax/instructions.html#vector-instructions for details.

[CountBleck]

This looks good.

Since we're here, I tried to look for some other errors, to see if this was a standalone issue...I don't think iNxM.any_true exists? Only v128.any_true and iNxM.all_true...this is my reference by the way.

Do you want to look through the file and find/fix those errors as well (that is, if you would like to)?

[chharvey]

@CountBleck you’re right, there are definitely discrepancies between the spec (which I think the index.d.ts file mirrors pretty well at first glance) and the README. They are probably due to careless copy-pasting when the vector instruction docs were added 6 years ago.

According to the W3C spec (which seems to be more official than the one at https://webassembly.github.io/spec/), only v128 has any_true, and only the “ishapes” (i8x16, i16x8, i32x4, i64x2) have all_true.

I can make those specific edits here if you want, but I think more time should be spent meticulously going over all the instructions for all the types and making sure the README matches — That might be beyond the scope of this PR. It might even involve some automation.

[CountBleck]

Fair enough. I'll go ahead and merge this in the meantime.

By the way, I would use https://webassembly.github.io/spec/core for the spec and not the W3C copy, since the former is more up-to-date.

On another note, this repo's docs and type declarations are mirroring the API Binaryen exposes (specifically, that file I sent you), not the spec directly, since this repo is adding docs/typing for/on top of that API.