downloading GP plots from the online version

[Bill Allombert <Bill.Allombert@math.u-bordeaux.fr>]

Dear PARI developers,

In the javascript version of GP:
<https://pari.math.u-bordeaux.fr/gpexp.html>
I have made an experiment to wrap plots in an <img> tag so that the
image can be downloaded (by right-clicking on it). 
It is a bit awkward to do because the SVG has to be converted to base64.

Please tell me if it works.
You can try:
ploth(x=1,100,[sqrt(2/(Pi*x)),besselj(0,x),-sqrt(2/(Pi*x))])

Cheers,
Bill.