export more built-in functions

[jaskang]

Is it possible to export the internal withFormat or rasterize? I use snapdom to implement a preview, and at this time, only toRaw or toSvg is needed. It is only necessary to convert to image when the user actually wants to export. If there is withFormat, the value of toRaw can be reused.

[tinchox5]

It's on roadmap #34

[tinchox5]

But take into account that my nemesis is Safari browser. In some occasions I had to force bitmap output even svg is selected