🚀 Feature: Add an API usage example in create and initialize modes

[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

Back before #668, this template used to include a nice little ## Usage section in the README.md:

Usage

npm i template-typescript-node-package

import { greet } from "template-typescript-node-package";

It would be included in the find-and-replace that switched template-typescript-node-package (now, create-typescript-app) to the user's new package name.

I removed that bit because it doesn't make much sense with --mode migrate. But for --mode create and --mode initialize it'd be really nice. So let's add it back in for just those modes.

Additional Info

Let's tackle this after #749.

[github-actions]

🎉 This is included in version v1.32.0 🎉

The release is available on:

• GitHub releases
• npm package (@latest dist-tag)

Cheers! 📦🚀