Fable async node IO

AsyncIo.fs

module AsyncIO
    let private readdir (dir: string): Promise<ResizeArray<string>> =
        Promise.Create(fun resolve fail ->
            Fs.readdir(U2.Case1 dir, fun err files ->
                if isDefined err then fail.Invoke(err) else resolve.Invoke(U2.Case1 files)))

    let private unlink (path: string): Promise<unit> =
        Promise.Create(fun resolve fail ->
            Fs.unlink(U2.Case1 path, fun err ->
                if isDefined err then fail.Invoke(err) else resolve.Invoke(U2.Case1 ())))