Interface to test and compare Excel files (.xls/.xlsx).

Changes for 1.54 - 2024-02-12T11:00:00Z

• Upgraded dependency on Spreadsheet:😛arseXLSX v0.31 and Spreadsheet:😛arseExcel v0.66 to pull the fix for CVE-2023-7101. https://blogs.perl.org/users/timothy_legge/2024/02/vulnerable-perl-spreadsheet-parsing-modules.html
• Updated copyright year.
• Tidied up unit test slightly.