[rahadbhuiya]

Summary

This PR implements comprehensive W3C CSS pseudo-classes support across the CSS parser, CSSOM data structures, specificity calculation, DOM query API, and selector matching engine.

Key Changes

• CSSOM & Specificity: Added PseudoClass enum (:hover, :active, :focus, :first-child, :last-child, :only-child, :empty, :root, :checked, :disabled, :enabled, Other). Aligned Selector::specificity to count each pseudo-class into class specificity (spec.1) per W3C specification.
• CSS Parser: Extended starts_simple_selector and parse_simple_selector to parse single and chained pseudo-classes (e.g. �utton:first-child:focus), with tolerant recovery for double-colon syntax.
• DOM State & Query: Added interactive hover/focus/active state flags and methods to ElementData and Dom (set_hovered, set_focused, set_active).
• Selector Matching: Implemented matches_pseudo covering structural element tree walks and form element state.
• Tests: Added comprehensive test coverage in parser_tests, dom::tests, and main.rs. Updated ROADMAP.md.