fix: enable wasip2 feature for wasm32-wasip2 target

After PR chipsenkbeil#51 added the requirement `any(windows, unix)` to expose native
and platform modules, and Rust changed WASI targets to set the `unix` cfg
(rust-lang/rust#147572), typed-path now attempts to compile code using
`std::os::wasi` for WASI targets. However, this is an unstable feature
requiring `#![feature(wasip2)]` when targeting wasm32-wasip2.

This commit adds the wasip2 feature flag conditionally only for wasip2
targets (target_env = "p2"), allowing the crate to compile with nightly
Rust for wasm32-wasip2 while maintaining compatibility with wasm32-wasip1
which does not have or need this feature.

Also fixes an unused import warning for `std::io` on wasm targets where
the `absolutize` function (which uses `io`) is not available.

Tested on both wasm32-wasip1 and wasm32-wasip2 targets - all 160 tests
pass on both platforms.

Author: cdmurph32

src/lib.rs

@@ -1,5 +1,6 @@
 #![cfg_attr(feature = "std", doc = include_str!("../README.md"))]
 #![cfg_attr(not(feature = "std"), no_std)]
+#![cfg_attr(all(target_os = "wasi", target_env = "p2"), feature(wasip2))]
 
 #[doc = include_str!("../README.md")]
 #[cfg(all(doctest, feature = "std"))]

src/typed/non_utf8/pathbuf.rs

@@ -1,8 +1,10 @@
 use alloc::borrow::Cow;
 use alloc::collections::TryReserveError;
 use core::convert::TryFrom;
+#[cfg(all(feature = "std", not(target_family = "wasm")))]
+use std::io;
 #[cfg(feature = "std")]
-use std::{io, path::PathBuf};
+use std::path::PathBuf;
 
 use crate::common::{CheckedPathError, StripPrefixError};
 use crate::no_std_compat::*;