make to_svg public

[ubamrein]

No need to have the to_svg function private, or is there?

https://github.com/askanium/rustplotlib/issues/1

[martinfrances107]

I think this is a good idea

here is a use case

I am using leptos ( a rust web framework inspired by react/sycamore )

For normal react applications, when working with d3 modules it is a standard pattern to use a createEffect() to modify the DOM after react has rendered a component.

if to_svg) were public then leptos apps would not have to use the equivalent createEffect() escape hatch

a string could be prepared as part of the normal render flow.