Introduce instructions for measuring test coverage

[kfcampbell]

This small PR adds a README update with instructions for measuring test coverage.

It also includes a go mod tidy update required for the module to build since the downgrade to Kiota v1.14.0.

[github-actions[bot]]

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[what-the-diff[bot]]

PR Summary

• Documentation Improvement A new section has been added to the main README file. This section provides instructions on building and testing our Software Development Kit (SDK). This will help users understand how they can test their developments more effectively.

• Module Addition A new module 'golang.org/x/sync v0.7.0' has been included in the project structure. This update in the 'go.mod' file ensures that all developers have access to the same set of functionalities, which aids in consistent development across the team.

• Sync of Dependencies The addition of 'golang.org/x/sync v0.7.0' module in the 'go.sum' file ensures that there is a record of the exact version of the module used. This makes sure that every time our project is built, it will use the same version of the module, hence avoiding any inconsistencies due to differences in module versions.