docs: document report formats and CSV header-only behavior

[kavya-seth-vns]

📖 Documentation Update: Report Formats

✨ Summary

This pull request improves the README by documenting DockSec's supported report formats in a dedicated Report Formats section.

✅ What's Included

• Added a dedicated Report Formats section to the README.
• Documented the supported output formats:
  • JSON – Machine-readable output for automation.
  • CSV – Tabular output for spreadsheets and reporting.
  • PDF – Human-readable report for sharing.
  • HTML – Interactive browser-based report.
• Clarified the expected header-only CSV behavior when no findings are present.
• Added references to the existing Machine-readable Output and SARIF Output sections instead of duplicating information.
• Maintained consistency with the existing README structure and writing style.

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📝 Type of Change

• Documentation update

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✅ Testing

• Verified Markdown formatting renders correctly.
• Verified internal links and section references.
• Reviewed for grammar, consistency, and readability.

Environment

• Operating System: Windows 11
• Python Version: N/A
• DockSec Version: Current main branch

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✔️ Checklist

• Documentation updated
• Self-review completed
• No warnings or errors introduced
• Spelling and formatting checked
• Follows the project's documentation style

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Closes #132

Thank you for reviewing this contribution! 🚀

[advaitpatel]

@kavya-seth-vns thank you for your PR however some other contributor has made the same changes. Could you please find any other issue and raise your PR again? Thank you!

[kavya-seth-vns]

@advaitpatel
Thank you for the clarification! I appreciate your feedback.

I'll look for another issue and submit a new PR soon.

Thanks!