src/vs/base/browser/ui/splitview/paneview.ts/PaneDraggable/onDragStart
class PaneDraggable:	private onDragStart(e: DragEvent): void {
		if (!this.dnd.canDrag(this.pane) || !e.dataTransfer) {
			e.preventDefault();
			e.stopPropagation();
			return;
		}

		e.dataTransfer.effectAllowed = 'move';

		if (isFirefox) {
			// Firefox: requires to set a text data transfer to get going
			e.dataTransfer?.setData(DataTransfers.TEXT, this.pane.draggableElement.textContent || '');
		}

		const dragImage = append(document.body, $('.monaco-drag-image', {}, this.pane.draggableElement.textContent || ''));
		e.dataTransfer.setDragImage(dragImage, -10, -10);
		setTimeout(() => document.body.removeChild(dragImage), 0);

		this.context.draggable = this;
	}