Support for wasm32-wasip2 target

[StuartHarris]

Compilation failure when targeting wasm32-wasip2 on nightly.

cargo +nightly build --target wasm32-wasip2

output:

...
   Compiling url v2.5.2
error[E0658]: use of unstable library feature 'wasip2'
    --> /Users/stuartharris/.cargo/registry/src/index.crates.io-6f17d22bba15001f/url-2.5.2/src/lib.rs:2835:9
     |
2835 |     use std::os::wasi::prelude::OsStrExt;
     |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
     |
     = help: add `#![feature(wasip2)]` to the crate attributes to enable
     = note: this compiler was built on 2024-08-10; consider upgrading it if it is out of date

error[E0658]: use of unstable library feature 'wasip2'
    --> /Users/stuartharris/.cargo/registry/src/index.crates.io-6f17d22bba15001f/url-2.5.2/src/lib.rs:2938:9
     |
2938 |     use std::os::wasi::prelude::OsStrExt;
     |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
     |
     = help: add `#![feature(wasip2)]` to the crate attributes to enable
     = note: this compiler was built on 2024-08-10; consider upgrading it if it is out of date

For more information about this error, try `rustc --explain E0658`.
error: could not compile `url` (lib) due to 2 previous errors