🚀 Feature: Add an option for a CODECOV_TOKEN secret

### Feature Request 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

Right now, this repo adds an `env: CODECOV_TOKEN` Addon to its Codecov Block:

https://github.com/JoshuaKGoldberg/create-typescript-app/blob/dd7547d43d503d22ab94080f1fc638661c878cba/src/integration.test.ts#L46-L50

That generates a bit extra `env` in the created `.github/workflows/ci.yml`:

https://github.com/JoshuaKGoldberg/create-typescript-app/blob/c0325c4ebdc35950583419b54527d85e6ed23cc7/.github/workflows/ci.yml#L68-L71

I added that because I keep hitting the Codecov rate limit for free open source repositories. But because this isn't a native `options` option I keep having to manually copy & paste these things on the CLI 😭. Irksome.

I'd like to add an optional `codecovToken` boolean option. That way I can fully create repos on the CLI that include this: `npx create-typescript-app --description "..." --repository "..." --codecov-token`.

### Additional Info

A nice stretch goal would be for `prepareOptions` / transition mode to fetch a codecov token from the API, and populate it as a repository secret if available... 🤔. If not done as part of this issue it can be a followup.

🎁