Allow to configure ignored extensions or prefixes for auto-upload

[Nowaker]

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

Nextcloud tries to upload files that aren't meant to be uploaded, even though they reside in the auto-upload directory.

Describe the solution you'd like

Allow to configure ignored extensions or prefixes for auto-upload.
In this case, that would be: .pending* to ignore.

Describe alternatives you've considered

There are no alternatives.

Additional context

That kind of setting belongs to per-directory settings. Not global ones. This is because .pending could be a legitimate file I want uploaded if present in a different directory.

[apparle]

It'll be useful for ignoring .trashed* also, which are generated by Google Photos app when it deletes the photos.

A generic ability to ignore specific regex of files will be very useful