Enable producing fully standalone html file
This optionally inlines all the plot images as data-uris. For SVG it tries to be smart and encode it directly as ascii SVG (SVG being natively ASCII) to save some space.
Note: this always inlines the layout images etc into the HTML file. I think this is fine to do as it only negligibly increases the HTML file size as opposed to inlining the plots. In principle, this can also be made optionally.