tt_to_tlgrtf() and tidytlg enhancements

[eanokian]

• In tt_to_tlgrtf() the Headers first col have whitespaces instead of actual indentation, but this is something that has to be fixed in tidytlg::gentlg_single(). Create a PR in tidytlg with this fix.
• colwidths when combined_rtf = TRUE are not vectorized