Support custom fonts in graph exports
When exporting graphs to any format, if you are using a custom font that is not installed on the user's computer (even if you are using the CSS @font declaration to include it for your site), the font will not be used on the exported chart.
You should be able to solve the issue by embedding the base64-encoded font in the SVG document prior to converting from SVG to whatever the desired format is (PNG, JPG, PDF, etc).
Note you must actually embed the font. Including it as a @font declaration in the SVG document does not work.