📝 Documentation: How to bump to a new major version

### Bug Report Checklist

- [X] I have pulled the latest `main` branch of the repository.
- [X] I have [searched for related issues](https://github.com/JoshuaKGoldberg/create-typescript-app/issues?q=is%3Aissue) and found none that matched my issue.

### Overview

Packages created by `create-typescript-app` start off on 0.x. But what's the right way in the CTA `release-it`-based system to bump to 1.x? And later on, 2.x? This should be documented.

### Additional Info

Example PR showing off this area: #531.

Folks often want to batch multiple breaking changes into a major. This should be figured out too.

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