grand_central_m4: Add an EIC example

[supersimple33]

Summary

I have added in my confirmed working eic example.

Checklist

• All new or modified code is well documented, especially public items
• No new warnings or clippy suggestions have been introduced - CI will deny clippy warnings by default! You may #[allow] certain lints where reasonable, but ideally justify those with a short comment.

Note

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  • Nothing else to do; your PR will likely be squashed down to a single commit.
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