Document scale_ggsurvfit() default y-axis limits

[DanChaltiel]

Hi Daniel,

I understand from #112 that scale_ggsurvfit() adding limits = c(0, 1) depends on the type of curve.

Shouldn't this be documented in ?scale_ggsurvfit?

This could also be an additional argument (as writing scale_ggsurvfit(y_scales=list(limits=c(0,1))) is a bit long).

For instance, expanding the y-axis is useful when comparing cumulative incidence plots.