0.21.0

• Added emacs-28 feature with Env::open_channel for pipe-based communication (Emacs 28+).
  • On Windows, this requires the module to be linked against the same C runtime as Emacs.
    • Keep in mind that Emacs officially supports MSVCRT, not the newer UCRT.
    • Caution: GNU toolchain uses gcc as the linker, so if mingw-w64-ucrt-x86_64-gcc is before mingw-w64-x86_64-gcc in $PATH, UCRT will be linked.