Refactor GitHub Actions for GitHub Pages deployment

[mattleibow]

This pull request updates the GitHub Actions workflow for documentation deployment, modernizing the process and improving security and reliability. The workflow now uses updated actions, sets explicit permissions for the GitHub token, and streamlines deployment to GitHub Pages.

Workflow modernization and deployment improvements:

• Updated the workflow to use newer versions of actions, including actions/checkout@v3 and actions/setup-dotnet@v3, and replaced the deprecated peaceiris/actions-gh-pages with actions/deploy-pages@v4 for GitHub Pages deployment.
• Added explicit permissions for the GitHub token to restrict access and enhance security during deployment (actions: read, pages: write, id-token: write).
• Introduced concurrency control to ensure only one deployment runs at a time, preventing overlapping deployments but allowing in-progress runs to finish.
• Changed the job name from deploy to publish-docs and set up the deployment environment for GitHub Pages, including the deployment URL output.
• Updated the steps to install .NET 8.x, update the docfx tool, build documentation, upload the artifact, and deploy to GitHub Pages using the latest recommended approach.