Fix selector-pseudo-class-no-unknown false positives for :open (#8184)

Author: lukewarlow

.changeset/tiny-lobsters-float.md

@@ -0,0 +1,5 @@
+---
+"stylelint": patch
+---
+
+Fixed: `selector-pseudo-class-no-unknown` false positives for `:open`

lib/reference/selectors.cjs

@@ -338,6 +338,7 @@ const pseudoClasses = uniteSets(
 		'modal',
 		'only-child',
 		'only-of-type',
+		'open',
 		'optional',
 		'out-of-range',
 		'past',

lib/reference/selectors.mjs

@@ -335,6 +335,7 @@ export const pseudoClasses = uniteSets(
 		'modal',
 		'only-child',
 		'only-of-type',
+		'open',
 		'optional',
 		'out-of-range',
 		'past',

lib/rules/selector-pseudo-class-no-unknown/__tests__/index.mjs

@@ -133,6 +133,10 @@ testRule({
 			code: ':popover-open {}',
 			description: 'explicit :popover-open test',
 		},
+		{
+			code: ':open {}',
+			description: 'explicit :open test',
+		},
 		{
 			code: ':active-view-transition, :active-view-transition-type() {}',
 		},