Add description about Cargo js feature for WebAssembly section

[Kazhuu]

Documentation improvement regarding #267.

[newpavlov]

You should add a clarification that the js feature SHOULD be enabled only in "application" crates. For library tests and benchmarks the feature should be enabled only for tests and benchmarks, not for the whole library.

[Kazhuu]

Okay I updated the doc specifically stating what you mentioned. I'm quite new to Rust in general so had to do some digging with this. Is it possible to enable specific feature when the crate type is binary for example? If yes, then example of this could be added to the docs.

For one of my own projects I've enabled js feature like this:

[dependencies.getrandom]
features = ["js"]

[josephlr]

@Kazhuu I've made some updates to the wording here. Hopefully this will help emphasize that this feature should generally be enabled on non-library crates (binary, benchmark, or test crates). I also removed the "Indirect Dependencies" Section as its now redundant.

I'll give @newpavlov a chance to review this. Note that the CI failure is caused by an unrelated nightly bug, see:

• CI is broken: "LLVM ERROR: dwo only supported with ELF and Wasm" rust-osdev/uefi-rs#494
• UEFI targets fail to compile: "LLVM ERROR: dwo only supported with ELF and Wasm" rust-lang/rust#101071
• Set DebuginfoKind::Pdb in msvc_base rust-lang/rust#101088

[Kazhuu]

Thanks @josephlr! Now the wording is a lot better and conveys more clearly what is needed. Even the original text I wrote is not there anymore I learned from this experience 👍