Document WebAssembly versions in /features/

If one wants to learn about engine support for specific WebAssembly features, I think https://webassembly.org/features/ is the best information there is; but it’s predicated around individual features, whereas the spec now seems to be versioned, and people will probably normally care more about a major version rather than an individual feature. It would be good to embrace that.

Here’s a sketch of the sort of thing I have in mind:

Two parts to this.

1. A new section for showing the earliest version of each engine supporting each major versions of WebAssembly, which I think is the summary most people want. I also suggest adding release dates for each engine—especially on the web, that’s normally more useful than version number.

2. Add a new header column at the start of the existing features table, grouping phase 5 features by which version of WebAssembly they’re first included in.

Aside: the present sorting of the features is not obvious; most are alphabetical, but they’re being sorted by something that may not even appear in the text, most notably “Non-trapping float-to-int Conversions” is being sorted as “saturatedfloattoint”. I think it would be worth choosing a manual ordering in some cases. The ordering of the groups in the individual features table is also interesting: as phases 5–1 are most mature to least mature, you might want the WASM version sort to ascend, so it’s showing 2.0 then 3.0 then finalised-but-not-yet-included-in-a-release then the degrees of not-finalised.

Start by reviewing the existing /features/ page and the current features table, then compare its engine-support data with the version-oriented structure described in the issue and mockup. Document earliest engine support and release dates for major WebAssembly versions, and group phase 5 features by their first included version while preserving a clear ordering. Confirm that the page presents both the new summary and revised table coherently.