chore: add rulers to vscode settings (#399)

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## PR Checklist

- [x] Addresses an existing open issue: fixes #370
- [x] That issue was marked as [`status: accepting
prs`](https://github.com/JoshuaKGoldberg/template-typescript-node-package/issues?q=is%3Aopen+is%3Aissue+label%3A%22status%3A+accepting+prs%22)
- [x] Steps in
[CONTRIBUTING.md](https://github.com/JoshuaKGoldberg/template-typescript-node-package/blob/main/.github/CONTRIBUTING.md)
were taken

## Overview

Added `"editor.rulers": [80]` to `.vscode/settings.json`.
This should add a ruler to indicate when a line break will occur.

Author: RNR1

.vscode/settings.json

@@ -4,6 +4,7 @@
 	},
 	"editor.defaultFormatter": "esbenp.prettier-vscode",
 	"editor.formatOnSave": true,
+	"editor.rulers": [80],
 	"eslint.probe": [
 		"javascript",
 		"javascriptreact",