--comments throws EISDir when a directory is specified in TSConfig include

[JoshuaKGoldberg]

🐛 Bug Report

• tslint-to-eslint-config version: 2.14.0
• ESLint version: n/a
• Node version: v20.2.0 (n/a)

Actual Behavior

$ npx tslint-to-eslint-config --comments

✨ 1 rule replaced with its ESLint equivalent. ✨

❗ 1 ESLint rule behaves differently from its TSLint counterpart ❗
  Check ./tslint-to-eslint-config.log for details.

⚡ 5 new packages are required for this ESLint configuration. ⚡
  npm install @typescript-eslint/eslint-plugin @typescript-eslint/parser eslint eslint-config-prettier eslint-plugin-prefer-arrow --save-dev
❌ 1 error running tslint-to-eslint: ❌
  Error: EISDIR: illegal operation on a directory, read

Expected Behavior

Shouldn't crash.

Reproduction

mkdir cool
touch cool/index.ts

// tsconfig.json
{
  "include": ["cool"]
}

As reported by @hyperupcall in #1717.

[JoshuaKGoldberg]

Published in tslint-to-eslint-config@2.14.1. Thanks @hyperupcall! 🥳