[Feature] Add datetime value to Sync->Backup->Export filename

[danjo]

Is your feature request related to a problem? Please describe.

Backup Export (to a local file) on Windows.

Export filename is fixed, when doing multi times goes like that

Then, import function not refer that filename, export-import filenames have no link, so export filename is not need fixed.

Describe the solution you'd like

Add datetime infomation to export filename

Additional context

Code I prefer like that https://github.com/danjo/stylebot/blob/devdanjo/src/options/utils.ts