Fix false positives for ui-* generic system font keywords in font-family-name-quotes

[nlydv]

What steps are needed to reproduce the bug?

1. Set the font-family-name-quotes rule to always-unless-keyword
2. Add one the following generic keywords in a font-family property:
   • ui-serif
   • ui-sans-serif
   • ui-monospace
   • ui-rounded
3. Run Stylelint on the file

What Stylelint configuration is needed to reproduce the bug?

{
    "rules": {
        "font-family-name-quotes": "always-unless-keyword"
    }
}

How did you run Stylelint?

CLI with stylelint style.css --config .stylelintrc

Which version of Stylelint are you using?

14.7.0

What did you expect to happen?

Stylelint would recognize ui-monospace et al. as a generic keyword that doesn't require quoting.

What actually happened?

A warning was given stating that it expected quotes around ui-monospace.

Does the bug relate to non-standard syntax?

No (see: https://www.w3.org/TR/css-fonts-4/#ui-serif-def and https://caniuse.com/extended-system-fonts).

Proposal to fix the bug

Add ui-serif, ui-sans-serif, ui-monospace, and ui-rounded to the list of generic font-family keywords such that they be recognized by rules such as font-family-name-quotes and any other relevant rules.

[jeddy3]

@nlydv Thanks for the report, using the template and for linking to the specs.

I've labelled the issue as ready to implement. Please consider contributing if you have time.

There are steps on how to fix a bug in a rule in the Developer guide.

It'll just be case of updating our reference list:

stylelint/lib/reference/keywordSets.js

Lines 93 to 100 in 91c3601

	keywordSets.fontFamilyKeywords = uniteSets(keywordSets.basicKeywords, [
	'serif',
	'sans-serif',
	'cursive',
	'fantasy',
	'monospace',
	'system-ui',
	]);