docs: add docs for test-set-config

[Sarthak160]

What has changed?

Please include a summary of the change.

This PR Resolves #(issue)

Type of change

Please delete options that are not relevant.

• Bug fix (non-breaking change which fixes an issue).
• New feature (non-breaking change which adds functionality).
• Breaking change (fix or feature that would cause existing functionality to not work as expected).
• Documentation update (if none of the other choices apply).

How Has This Been Tested?

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Checklist:

• My code follows the style guidelines of this project.
• I have performed a self-review of my own code.

[Copilot]

Pull Request Overview

This PR adds comprehensive documentation for the test-set configuration file feature in Keploy version 3.0.0. The documentation explains how to use config.yaml files alongside test data to customize runtime parameters on a per-test-set basis.

• Adds complete documentation for test-set configuration functionality
• Provides practical examples and troubleshooting guidance
• Includes best practices for managing test-set specific configurations

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[Copilot]

Inconsistent indentation in the directory structure example. Use consistent spacing (either tabs or spaces) for proper formatting in documentation.

Suggested change

	my-test-set/
	mock.yaml # Recorded mocks for this test-set
	config.yaml # Test-set specific configuration (optional)
	... # Any other assets
	my-test-set/
	mock.yaml # Recorded mocks for this test-set
	config.yaml # Test-set specific configuration (optional)
	... # Any other assets

[Copilot]

The text 'common example -' should be capitalized and have proper punctuation: 'Common example:'

Suggested change

	common example -
	Common example: