Save as SVG or PNG does not maintain the fonts

[jmhorcas]

The font of the title (and possibly the font of the properites) is lost when saving the label as SVG or PNG.

[jmhorcas]

We need to include the font in the SVG as follows:

chart.append('defs')
      .append('style')
      .attr('type', 'text/css')
      .text("@import url('https://fonts.googleapis.com/css2?family=Libre+Franklin:wght@900');");

Actually the font for the title is set to "Libre Franklin 900" but the original is "Franklin Gothic Heavy".
For the body of the labels (and properties) the original font is Helvetica regular, but this is not set currently, and need to be explicitly set in the SVG. However, the Helvetica font is not available in Google Fonts and the alternatives are ugly.

[jmhorcas]

Currently, SVG maintains the fonts but not for PNG.