[DOCS] Reorder some lines in the class diagram (part 13)

This is in preparation for #1298.

Author: oliverklee

README.md

@@ -788,8 +788,8 @@ classDiagram
     SourceException <|-- UnexpectedTokenException: inheritance
     CSSElement <|.. Value: realization
     Positionable <|.. Value: realization
-
     Value <|-- ValueList: inheritance
+
     CSSList ..> CSSList: dependency
     CSSList ..> Comment: dependency
     CSSList ..> RuleSet: dependency