Plotting trace: add support for LaTeX when specifying the name of a plot trace

[FinbarArgus]

Allow mapping from user define Latex plot_name to html.

[agarny]

Right now, the name of a plot trace can include HTML code (e.g., <i>I<sub>Na</sub></i>), but it would be good to be able to include some LaTeX code too (e.g., $I_{\mathrm{Na}}$).

It looks like this can be done using https://latex.js.org/.