Add Kevin Shaffer-Morrison to humans.txt (#51015)

Adding Kevin Shaffer-Morrison to humans.txt as he just joined the team!

## Checklist

Check all before review:

- [x] I have read
[CONTRIBUTING.md](https://github.com/supabase/supabase/blob/master/CONTRIBUTING.md)
- [x] If I wrote a new docs topic or edited an existing topic, I used
the `/write-the-docs` or `/edit-the-docs` skill, which applies the docs
[style
guide](https://github.com/supabase/supabase/tree/master/apps/docs/style-guide)


<!-- This is an auto-generated comment: release notes by coderabbit.ai
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## Summary by CodeRabbit

* **Documentation**
* Added Kevin Shaffer-Morrison to the public team listing. No other
documentation or public-facing declarations changed.

<!-- end of auto-generated comment: release notes by coderabbit.ai -->

apps/docs/public/humans.txt

@@ -189,6 +189,7 @@ Keith Fiske
 Kemal Y
 Kevin Brolly
 Kevin Grüneberg
+Kevin Shaffer-Morrison
 Kevin Strong-Holte
 Kostas Botsas
 Krishna Sai Vandavasi