feat: added description to generated sample excel file (#786)

[Sidd-77]

Description

This PR addresses issue #786 by adding a description section to the generated sample Excel file. To achieve this, the following changes were made:

• Integrated the @eyeseetea/xlsx-populate library to enhance Excel file manipulation and generation.
• Created a backup of the existing implementation as old-file.service.ts to preserve the previous approach for reference and rollback purposes.

Changes Made

• Added a description section to the generated Excel files for better clarity and usability.
• Updated the file generation process using @eyeseetea/xlsx-populate for improved performance and functionality.
• Maintained the old implementation separately in old-file.service.ts for legacy support.

Testing

• Verified that the new description appears correctly in the generated Excel file.
• Ensured that the backup file (old-file.service.ts) remains functional if needed.

Related Issue

• Closes #786