Dashed ListStyle support for QTextListFormat

 We have encountered a limitation in the QTextListFormat class where there is no built-in support for dashed list styles. QTextListFormat provides several predefined styles for numbering and dot lists, such as `ListDisc`, `ListCircle`, `ListSquare`, `ListDecimal`, and `ListLowerAlpha`, among others. However, there isn't an option for creating lists with a dashed style, which is commonly used in various design and document formats.

So please add the support for dashed list style in QTextListFormat.