Add calculation of the directory size in a file panel.

The part you want to Enhancement Add calculation of the directory size in a file panel. feature use cases:

• The hotkey for calculating size of focused directory is "space".
• When a calculating is in process column size for directory must have "???".
• If user haven't enough rights to enter into directory spf must notify by a modal panel
• If user haven't enough rights for some files or dirs in directory the result must be shown with "?". F.e. "? 8.00 Kib". It's mean that result contains only a part of files inside the target .directory
• A size calculation must be asynchronous.

example in TC

Why it is necessary to enhancement helps find big or small directories :)

Additional context continue of https://github.com/yorukot/superfile/issues/1204