Hello,

I would like to visualize a probability density function, and associated samples plotted along the x axis.

```
using Plots
N = 100
X = randn(N)
xgrid = -5.0:0.01:5.0
plt = plot(xgrid, pdf.(Normal(), xgrid), ylim = (-Inf,Inf), label = "pdf")
scatter!(plt, X, zeros(N), markersize = 10, label = "Samples")
plt
```

Is it possible to show the entire markers (instead of the truncated circles) for the samples along the x axis?