🛠 Tooling: Use the create engine for initial/sample file creation

[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

Splitting out of #1181: I'm onboarding this project to the new "create" engine in https://github.com/JoshuaKGoldberg/create. #1670 added usage of file creations. Another step will be using the engine to boostrap initial/sample files. In this repo that's:

• src/greet.ts
• src/greet.test.ts
• src/index.ts
• src/types.ts

This may also be the place to specify logic for deleting existing files. If someone uses CTA as a GitHub template repository and then runs the initialize script, the src/ directory should have all of the existing CTA blockstuffs removed. It should instead only have those files.

Additional Info

Linked issue on create: JoshuaKGoldberg/create#25

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