Add new methods and enhance existing documentation for Excel manipulation - Introduced SetColLevel method for defining column grouping levels. - Added SetDateTime method for setting date and time in cells. - Implemented SetHeader and SetFooter methods for configuring print headers and footers. - Created SetPagOrientation method to define page orientation for printing. - Added SetPlanAt method for positioning in existing sheets by index or name. - Implemented SetPrintArea and SetPrintTitles methods for defining print areas and titles. - Introduced SetRowH method for setting row heights. - Added SetStyle method for applying styles to cells or ranges. - Implemented SetValueBulk method for bulk value insertion. - Enhanced cell manipulation methods (Cell, GetValue) to use custom.excel.Xlsx. - Added mergeCells method for merging cell ranges. - Updated New method to include processing type options. - Enhanced NewStyle method for style creation. - Updated Pos and PosR methods to support chaining. - Added showGridLines method to toggle grid line visibility. - Enhanced cell protection methods for better usability.