Feature request: XPlot.Plotly -- separate Chart.WithLayout with smaller functions

When using XPlot,Plotly, one has to create a layout val even just to change a minor element. Since the Layout type contains so many components, I think it would be a good idea to have separate functions to allow users to set each value, such as:

```
Scatter(x=x, y=y)
|> Chart.Plot
|> Chart.WithYaxis Yaxis(tickformat=".0%")
```