docs: document report formats and CSV header behavior

[ShrijalDubey]

Description

Added a dedicated "Report Formats" subsection to the README under the Quick Start area to clarify the available export configurations and document unique output behaviors.

Closes #132

Type of Change

• Bug fix
• New feature
• Breaking change
• Documentation update
• Code style update (formatting, renaming)
• Code refactoring (no functional changes)
• Performance improvement
• Test update
• Build / CI configuration
• Security fix

How Has This Been Tested?

Verified by previewing the Markdown rendering locally to ensure headers, bullet points, code references, and anchor links resolve correctly.

• Unit tests
• Manual testing

Test Configuration:

• Python version: 3.x
• Operating System: Windows (PowerShell)
• DockSec version: Local dev branch

Checklist

• Code follows the style guidelines of this project
• Self-review completed
• Hard-to-understand areas are commented
• Documentation updated where needed
• No new warnings or errors introduced
• Tests added that prove the fix or feature works
• All existing tests pass
• Dependent changes have been merged and published
• Spelling checked

Screenshots (if applicable)

Related Issues / PRs

• Relates to [GOOD FIRST ISSUE] Document --format output formats and CSV header-only behavior in README #132
• Depends on #

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By submitting this pull request, I confirm that my contribution is made under the terms of the MIT license.

[advaitpatel]

lgtm

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
⚠️ Please upload report for BASE (main@b62a7d7). Learn more about missing BASE report.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #136   +/-   ##
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  Coverage        ?   78.37%           
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  Files           ?       26           
  Lines           ?     4028           
  Branches        ?        0           
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  Hits            ?     3157           
  Misses          ?      871           
  Partials        ?        0           

Flag	Coverage Δ
unittests	78.37% <ø> (?)

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