[Request] Add silent flag

[ParadoxLeon]

It would be nice if the desktop app had a --silent flag (or whatever) so it runs in background.
That would make auto-starting the app more cleaner.

[johaven]

Feature added in v1.3.0, an option is available in the app menu.

You can also use an environment variable or a command-line flag to control this behavior -> https://sync-in.com/docs/user-guide/sync#launch-the-desktop-app-in-hidden-mode-on-first-startup