css_conditional_3 library Null safety

CSS Conditional Rules Module Level 3

https://drafts.csswg.org/css-conditional-3/

Classes

CSSConditionRule
An object implementing the interface represents a single condition CSS at-rule, which consists of a condition and a statement block. [...]
CSSMediaRule
The interface represents a single CSS @media rule.
CSSSupportsRule
The interface represents a single CSS @supports at-rule.