1.0.0 September 7 2020

• Added support for worksheet conditional formatting.

• Added performance optimization for search for control characters in strings
  in worksheet_write_string().

• Made lxw_datetime_to_excel_datetime() a function public.

• There are now over 1000 test cases, including 650 tests that compare the
  output from libxlsxwriter, byte for byte, against test files created in
  Excel. This is also the 100th release of libxlsxwriter.