Add Dialog for displaying SVG side-by-side using lunasvg and nanosvg

[KeyWorksRW]

Description:

While most SVG files will display correctly in wxWidgets 3.2, there are some that do not. That difference could become even more pronounced in the future if lunasvg adds support for more of the SVG 1.1 (e.g. embedded images, filters, text, etc.). It might be useful to add a dialog under the Tools menu that could display an SVG file using both rendering engines side-by-side. This would allow users to see how their SVG files will be rendered in wxWidgets 3.2 versus wxWidgets 3.3.