Fix wasm examples failing to compile

[Liamolucko]

Description
The web examples were broken by 476b6a1, because apparently enabling a feature in any package enables it for the whole workspace, and the wasm examples fail to compile with Vulkan enabled.

It wasn't failing in CI because CI specifies -p wgpu, which seems to stop wgpu-info's enabling of features having an effect.

Testing
If you try to run a wasm example on master, it'll fail to compile due to libloading being included as a part of vulkan support, which doesn't support wasm. With this change, it works again.

[cwfitzgerald]

That's some wild stuff, my worry though now is that cargo build --target wasm32-unknown-unknown will now fail to compile as wgpu-info won't compile. Maybe the solution is to have the features enabled on non-wasm only (so have two wgpu deps, one unconditionally with no features, and one with these two features)

[kvark]

@cwfitzgerald do we need wgpu-info on the Web at all? If not, we could add a top-level guard on wgpu-info's code to only work on native, and then it will happily compile (as an empty crate) for the web.

[cwfitzgerald]

No we don't, so that would be a perfectly viable solution too.

[kvark]

@Liamolucko would you be open to making this change to wgpu-info, making it an empty crate for wasm targets?

[Liamolucko]

@Liamolucko would you be open to making this change to wgpu-info, making it an empty crate for wasm targets?

Okay, done.

[cwfitzgerald]

LGTM