[mkdocs] - plotly.js loaded many times

[LiamConnors]

In the existing docs if you go to a page like https://plotly.com/javascript/3d-axes/
We can see although there are six examples, plotly.js is loaded from the cdn once:

On the mkdocs site however it looks like it loads multiple times

[camdecoster]

Good catch. I thought that might happen once the live examples got fixed. We can work around it.