CopyMove mode with file-picker

[rotdrop]

Hi,

I stumbled over the issue that the current implementation does not give access to the user-chosen operation mode (copy vs. move). Or am I wrong? IMHO the current approach

https://github.com/nextcloud/nextcloud-dialogs/blob/e61b9da780e80b02ba412e20375395812cbebc83/lib/filepicker.ts#L40-L45

hides this information which in principle is passed as second argument to the res callback, which however is the callback of the promise. And a promise is resolved with only a single argument. Hence this information is not passed on to the calling code.