WASM and MacOS target not built on docs.rs

[daxpedda]

I believed that #3462 would add the wasm32-unknown-unknown successfully to docs.rs builds, but it didn't.

See https://docs.rs/wgpu/0.15.1/wgpu/.

Trying to dig into it further, I noticed that previous versions didn't succeed in building x86_64-apple-darwin either.
Unfortunately https://docs.rs/crate/wgpu/0.15.1/builds/740775 doesn't provide any further help.

[daxpedda]

Just stumbled on https://docs.rs/crate/wgpu-core/0.15.1/builds/740772.

[daxpedda]

The problem should be #3465.
At the end of all of this we should probably add doc testing for all the targets to the CI.