LibWeb: Parse CSS text-decoration-thickness property

Author: https://github.com/krkk
Commit: 0f7156ed81
Pull-request: https://github.com/SerenityOS/serenity/pull/12915
Reviewed-by: https://github.com/AtkinsSJ ✅

Userland/Libraries/LibWeb/CSS/StyleValue.cpp

@@ -1319,7 +1319,7 @@ String PositionStyleValue::to_string() const
 
 String TextDecorationStyleValue::to_string() const
 {
-    return String::formatted("{} {} {}", m_line->to_string(), m_style->to_string(), m_color->to_string());
+    return String::formatted("{} {} {} {}", m_line->to_string(), m_thickness->to_string(), m_style->to_string(), m_color->to_string());
 }
 
 String TransformationStyleValue::to_string() const