Add Fs.opendir and Fs.Dir

[exoego]

They were added in Node.js v12.12.0.

• https://nodejs.org/api/fs.html#fs_fs_opendir_path_options_callback
• https://nodejs.org/api/fs.html#fs_fs_opendirsync_path_options
• https://nodejs.org/api/fs.html#fs_fspromises_opendir_path_options
• https://nodejs.org/api/fs.html#fs_class_fs_dir