This is the code I use:
using PlotlyLight;
preset.template.plotly_dark!();
p = plot(x = 1:20, y = cumsum(randn(20)), type="scatter", mode="lines+markers");
p.layout.title.text = raw"$\frac{1}{2}$"
p
The result:

On VS Code 1.90.2 (Latest) with the Julia VS Code Extension 1.79.2 (Latest).