This function creates border styles for a cell in a spreadsheet. Border styles can be any of the following: "none", "thin", "medium", "dashed", "dotted", "thick", "double", "hair", "mediumDashed", "dashDot", "mediumDashDot", "dashDotDot", "mediumDashDotDot", "slantDashDot". Border colors can be created with wb_color().