Moderators Note:
Is plugin can now be found here:
https://forums.getpaint.net/topic/117086-scalable-vector-graphics-filetype-alternative-plugin-svg-svgz/
For some reason the plugin isn't able to open SVG files exported from Adobe Illustrator. All the shapes turn out black. Searching the forums I could only find this release. Fortunately a Google search came up with this one released on Github that works for me: https://github.com/otuncelli/Scalable-Vector-Graphics-Plugin-for-Paint.NET/releases