[Docs] Hide the navigation and toc sidebars on home page

[hmellor]

Since we no longer duplicate the nav on the home screen, the nav only contains a lonely link to Home.

This PR removes both sidebars from the home page to reduce the clutter and prevent users wondering where the rest of the links are on the left (they're on the top!)

[github-actions]

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[gemini-code-assist]

Code Review

This pull request aims to reduce clutter on the documentation's home screen by hiding the navigation and table of contents sidebars. The change is implemented by adding YAML frontmatter to docs/README.md, which is the correct approach for the mkdocs-material theme being used. The modification is sound and achieves the stated goal without any apparent side effects. The top navigation remains available, ensuring site navigation is not hindered. I have no specific feedback as the change is correct and well-implemented.