How to build ggsurvfit?

[ddsjoberg]

at the moment we use ggsurvfit_build(), but we could perhaps use methods for ggplot_build() or ggplot_gtable() that would build, and the implication may be that the patchwork operators would then build the object for us.

[ddsjoberg]

We could perhaps use the default ggplot_build() method, and implement a ggplot_gtable() method and in this method we would aligning the risktables and plots and stacking using patchwork.

We may need a ggplot_build() that would preserve the class, because gtable function is called after the build