QUploader: Support async filter or trigger addFiles instead of addFilesToQueue in drag-and-drop flow

[DouglasCalora]

In my custom uploader, I need to process files before sending them to the uploader.

To achieve this, I had to create my own addFiles method using a native input and then call Quasar’s addFiles internally.

However, when using drag and drop, I can’t intercept the files — and I can’t use the filter prop either, since it doesn’t support async functions.

I also can’t override the addFiles method because Quasar doesn’t call it for drag-and-drop; instead, it uses addFilesToQueue.

It would be great if the filter prop could support returning a Promise for async processing before uploading, or alternatively, if addFiles could be called inside the onDrop handler instead of addFilesToQueue.