Add libc feature to enable crossterm's libc backend

[NiltonVolpato]

This adds a libc feature that enables crossterm's libc feature, allowing reedline to work in environments where rustix's raw syscall approach fails.

Motivation

When running under x86 emulation (e.g., CheerpX/WebVM, QEMU user-mode), reedline fails with:

Reedline error: Invalid argument (os error 22)

The root cause is that rustix uses the TCGETS2 ioctl via raw syscalls, which some emulators don't implement. See:

• https://bugs.launchpad.net/ubuntu/+source/qemu/+bug/2133804

Crossterm has a libc feature that uses libc's tcgetattr instead, which falls back to TCGETS and works in these environments.

Changes

• Adds libc feature that enables crossterm/libc

Usage

reedline = { version = "...", features = ["libc"] }

[fdncred]

Seems reasonable. Just need to get the CI green, which I think is because of the lock file not being included in the PR.

[fdncred]

update the lock file and we'll be good to go. Is that something you can do @NiltonVolpato ?

[fdncred]

Thanks