feat: add notice to home page

[scoltman]

Fixes #162.

Adding a simple notice to the home page to say it's in development.

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Pull request checklist

• [ ] I have linked my PR to an issue
• [ ] I’ve used conventional commits
• [ ] My branch is up-to-date with main
• [ ] Where appropriate, I have added or updated tests
• [ ] Where appropriate, I have updated documentation to reflect my changes

[scoltman]

I think we should clarify "Raphael can make mistakes" like ChatGPT does.

okay the copy has been updated