[Update] README file with updated documentation

[dutt0]

Overview/Summary

README file is updated to newer content.

This PR fixes/adds/changes/removes

This pull request includes the updated content in the README file and updated links to TBS GR policy v1.0 and gcxchange documents (Architecture, Installation Playbook, and Remediation Playbook)

Breaking Changes

Testing Evidence

As part of this Pull Request I have

• [x] Checked for duplicate Pull Requests
• [ ] Associated it with relevant GitHub Issues
• [x] Ensured my code/branch is up-to-date with the latest changes in the main branch
• [ ] Performed testing and provided evidence.
• [x] Updated relevant and associated documentation.
• [ ] Ensure PowerShell module versions have been updated (manually or with the ./tools/Update-ModuleVersions.ps1 script)