🛠 Tooling: Add a bot thanking people for their first contribution

[JoshuaKGoldberg]

Bug Report Checklist

• I have tried restarting my IDE and the issue persists.
• I have pulled the latest main branch of the repository.
• I have searched for related issues and found none that matched my issue.

Overview

This is a nice tip I was taught recently: it'd be great to have a bot that congratulates people on their first merged pull request. It can mention...

• General happiness and joy, including some happy emojis
• Encouragement to try more issues
• ...is there anything else?

Additional Info

No response

[JoshuaKGoldberg]

https://github.com/marketplace/actions/first-contribution looks like a good bot here. :)

I bet it could even integrate with options.guide...