Fix screenOverlayContainer type in docs
Fix screenOverlayContainer type in docs

CesiumGS/cesium,likangning93/cesium,CesiumGS/cesium,CesiumGS/cesium,AnalyticalGraphicsInc/cesium,CesiumGS/cesium,likangning93/cesium,likangning93/cesium,likangning93/cesium,CesiumGS/cesium,likangning93/cesium,AnalyticalGraphicsInc/cesium