src/vs/workbench/contrib/terminal/browser/terminalInstance.ts/TerminalInstanceDragAndDropController/onDragOver
class TerminalInstanceDragAndDropController:	onDragOver(e: DragEvent) {
		if (!e.dataTransfer || !this._dropOverlay) {
			return;
		}

		// Dragging terminals
		if (containsDragType(e, TerminalDataTransfers.Terminals)) {
			const side = this._getDropSide(e);
			this._dropOverlay.classList.toggle('drop-before', side === 'before');
			this._dropOverlay.classList.toggle('drop-after', side === 'after');
		}

		this._dropOverlay.style.opacity = '1';
	}