Lunacy

Lunacy is a native windows app that works offline. You can open, edit and save .sketch files, draw join align objects use a basic typography tool and export assets in png and svg format.

UI is very effective and it supports XAML, CSS. It also offers the option of visual transfer to CDN.

It supports vector illustration.This character designed by Balram Khichar. You can check other UI Kits, icons and vectors from Sketch app sources

Also, you can report bugs to the community and votes for the features. Additionally, it is free