plotlyjs.jl figures not rendering when exported as html

**Describe the bug**

Background: I work at Plotly, and I'm trying to figure out how to better document the `plotlyjs.jl` library alongside the `plotly.jl` library.

Issue: Figures I create using `plotlyjs.jl` in a Jupyter Notebook do not render when exported as `.html` files using `nbconvert` because `WebIO` is not present in the runtime.

My question Is: how can I get the figures I create with `plotlyjs.jl` in a jupyter notebook to render when exported to `.html`?

Screenshot:

Steps to Reproduce: Create a figure using PlotlyJS.jl in a Jupyter Notebook with a Julia 1.4.1 kernel, then use `jupyter nbconvert` to transform the notebook into an .html file.

**Version info**