ticklabeloverflow does not work for PlotLayoutAxis

Hello,

there are actually 2 issues, and I suppose the second might be related to plotly rather than StipplePlotly:

Issue 1:
Even though it says so in the docstring, PlotLayoutAxis does not have a field named "ticklabeloverflow". Consequently, there is an error if one tries to assign a value to it.

Issue 2:
I tried to fix the issue by adding the following line to the struct definition of PlotLayoutAxis in Layouts.jl (copied from the definition of ColorBar):
```julia
ticklabeloverflow::Union{String,Nothing} = nothing # "allow" | "hide past div" | "hide past domain"
```
I also added `:ticklabeloverflow` to the list given to `optionals!`

Unfortunately, changing this field value then doesn't seem to have any effect on the flow of my tick labels. I am not sure whether my "fix" was executed incorrectly or whether this is a plotly issue.

Both issues don't really affect me though, because I can just as well use `automargin = true`

Cheers