__wasi_prestat_t documentation is missing

[wanderer]

the description of __wasi_prestat_t from __wasi_fd_prestat_get seems to missing. Its defined here in wasmtime but I'm not sure why __wasi_preopentype_t pr_type; can't just be a __wasi_filetype_t

[sunfishcode]

This was fixed in c760e95.

pr_type isn't a __wasi_filetype_t because in the future we may have more kinds of preopen types, like preopened clocks or other things. We could stand to have more preopen types than we do now though.