src/vs/workbench/contrib/terminal/browser/terminalInstance.ts/TerminalInstanceDragAndDropController/onDragEnter
class TerminalInstanceDragAndDropController:	onDragEnter(e: DragEvent) {
		if (!containsDragType(e, DataTransfers.FILES, DataTransfers.RESOURCES, TerminalDataTransfers.Terminals, CodeDataTransfers.FILES)) {
			return;
		}

		if (!this._dropOverlay) {
			this._dropOverlay = document.createElement('div');
			this._dropOverlay.classList.add('terminal-drop-overlay');
		}

		// 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');
		}

		if (!this._dropOverlay.parentElement) {
			this._container.appendChild(this._dropOverlay);
		}
	}