v0.2.0

Changelog

• Improve efficiency of close_open_fds() if keep_fds is sorted
• Add Windows support (closes file descriptors only, not file handles)
• Disable /proc/self/fd check on WSL 1, where it's broken (it works on WSL 2)
• Open all file descriptors as O_CLOEXEC (just in case)
• Make tests stricter