feat: clarify option selection mechanism (#1122)

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## PR Checklist

- [x] Addresses an existing open issue: fixes #1121
- [x] That issue was marked as [`status: accepting
prs`](https://github.com/JoshuaKGoldberg/create-typescript-app/issues?q=is%3Aopen+is%3Aissue+label%3A%22status%3A+accepting+prs%22)
- [x] Steps in
[CONTRIBUTING.md](https://github.com/JoshuaKGoldberg/create-typescript-app/blob/main/.github/CONTRIBUTING.md)
were taken

## Overview

<!-- Description of what is changed and how the code change does that.
-->
This PR adds the text `You can press ↑ and ↓ on the keyboard to change
the selected item, then space to select.` to the creation mechanism.

:sunflower:

---------

Co-authored-by: Josh Goldberg ✨ <[email protected]>

Author: johnnyreilly

src/shared/options/augmentOptionsWithExcludes.ts

@@ -213,7 +213,7 @@ export async function augmentOptionsWithExcludes(
 					await prompts.multiselect({
 						initialValues: exclusionKeys,
 						message:
-							"Select the tooling portions you'd like to remove. All are enabled by default.",
+							"Select the tooling portions you'd like to remove. All are enabled by default. Press ↑ or ↓ to change the selected item, then space to select.",
 						options: Object.entries(exclusionDescriptions).map(
 							([value, { hint, label }]) => ({
 								hint,