Add WebAssembly features as a new category

[queengooborg]

This PR adds a brand new category for WebAssembly features -- that is, features within the WebAssembly code itself rather than just the JavaScript API. The results were collected by the mdn-bcd-collector project (v10.0.0).

CC @MendyBerger

[Elchi3]

Some questions:

• Unlike other top-level categories, the webassembly features are added flat without any folders or categories. Will this scale?
• Are there spec_urls for these features? It says standards_track true, so I guess there must be.
• Are there mdn_urls for these features?
• Will this PR mean a major version bump for BCD given a new top-level tree is added?

[queengooborg]

• Unlike other top-level categories, the webassembly features are added flat without any folders or categories. Will this scale?

When @MendyBerger wrote the PR to add this category into the collector, they used webassembly.features.* instead of just webassembly.*, but I later thought a subfolder was redundant. Happy to add it back though!

• Are there spec_urls for these features? It says standards_track true, so I guess there must be.

@MendyBerger, you know a lot more about WebAssembly than we do -- do you know if there are spec URLs associated with these features?

• Are there mdn_urls for these features?

Not yet as far as I know, but I believe there are plans to write them!

• Will this PR mean a major version bump for BCD given a new top-level tree is added?

Not a major version, but a minor version, since it's adding a new backwards-compatible feature!

[MendyBerger]

Subfolder:
I don't expect too many features on the wasm side of things. It's pretty low level, so development of new features are probably going to slow down over time. But I'm not working on the specs so take my opinion with a grain of salt.
I don't think that a subfolder would make a huge difference either way. Whatever works I guess 🤷 .

Spec urls:
There sure are, I can add them in.
I'm assuming they would go in the wasm.json file in collector, right?

[queengooborg]

There sure are, I can add them in.
I'm assuming they would go in the wasm.json file in collector, right?

Actually, the collector wouldn't deal with spec URLs; we'd want to add them right here in BCD!

Would you be down to submit a PR to this branch or send me a patch file so I can apply the appropriate changes? (Alternatively, if you'd like to send a list that maps spec URLs to BCD features, I can add those in too!)

[Elchi3]

Thanks for your comments!

• no sub folders then
• minor version bump
• let's add spec_urls before merging this.

[MendyBerger]

@queengooborg see queengooborg#53

[queengooborg]

Got the spec URLs added, and made the appropriate changes to typedefs, the readme and more -- this is now ready to merge!

[Elchi3]

Thanks, let's do this then 👍