def header_footer
      @header_footer ||= HeaderFooter.new
      yield @header_footer if block_given?
      @header_footer
    end
Options for headers and footers.
@example
wb = Axlsx::Package.new.workbook
# would generate something like: "file.xlsx : sheet_name 2 of 7 date with timestamp"
header = {:different_odd_ => false, :odd_header => "&L&F : &A&C&Pof%N%R%D %T"}
ws = wb.add_worksheet :header_footer => header

@see HeaderFooter#initialize
@return [HeaderFooter]