🛠 Repo: Enable ESLint's recommended rules for JS

[JoshuaKGoldberg]

Tooling Suggestion Checklist

• I have tried restarting my IDE and the issue persists.
• I have pulled the latest main branch of the repository.
• I have read and agree to Mocha's Code of Conduct and Contributing Guidelines
• I have searched for related issues and issues with the faq label, but none matched my issue.
• I want to provide a PR to resolve this

Overview

Back in #5060, I'd added an ESLint config but not enabled any of the recommended rules from js.configs.recommended. The rules object is overridden by our custom settings:

mocha/eslint.config.js

Lines 11 to 26 in 3c191c0

	module.exports = [
	{
	...js.configs.recommended,
	languageOptions: {
	ecmaVersion: 2020,
	globals: {
	...globals.browser,
	...globals.node
	},
	sourceType: 'script'
	},
	rules: {
	'no-var': 'off',
	strict: ['error', 'global']
	}
	},

Additional Info

The fact that I missed this and no reviewers caught it is a testament to the ... joy of being new adopters of flat config. 🙃

[voxpelli]

Perhaps we could go with https://github.com/neostandard/neostandard as a base? Considering that semistandard was what was used before #5060 and neostandard now is an option?

[JoshuaKGoldberg]

I'm tentatively in favor, but haven't dug into neostandard enough to have a super informed opinion. Is it a superset of ESLint's recommended JS rules, roughly? From what I've seen it seems like it'd be a good next step after this?

[Uzlopak]

I think we should move to neostandard.