NPOI 设置合并区域的边框

参考资料：https://blog.csdn.net/keenrob/article/details/102953239

1  RegionUtil.SetBorderLeft(1, region, sheet, workbook)//左
2  RegionUtil.SetBorderRight(1, region, sheet, workbook)//右
3  RegionUtil.SetBorderTop(1, region, sheet, workbook)//顶
4  RegionUtil.SetBorderBottom(1, region, sheet, workbook)//底