15.0.0

• Removed: stylelint less than 16.13.0 from peer dependencies.
• Removed: color-no-invalid-hex rule.
• Removed: function-linear-gradient-no-nonstandard-direction rule.
• Removed: function-no-unknown rule.
• Removed: unit-no-unknown rule.
• Changed: string-no-newline rule option to { ignore: ['at-rule-preludes', 'declaration-values'] }].
• Added: at-rule-descriptor-no-unknown rule.
• Added: at-rule-descriptor-value-no-unknown rule.
• Added: at-rule-no-deprecated rule.
• Added: at-rule-prelude-no-invalid rule.
• Added: declaration-property-value-keyword-no-deprecated rule.
• Added: declaration-property-value-no-unknown rule.
• Added: media-feature-name-value-no-unknown rule.