Make performance metrics graphs (and maybe other visualizers) exportable to png, jpg..

Hello, I think this is not currently implemented, or at least I was unable to find it.

I was recently using the GUI and was trying to share or show the performance metric graphs. I found it kind of difficult to share them and thought that it would be great if there was an option to generate pngs, jpgs etc...

This would make Autosubmit and its GUI have bigger reach out, as the metrics produced could be shared much easily and even be used in reports, papers, etc...