Add examples/pictures for curve types, especially the surface ones.

[luciansmith]

This would still be nice if anyone has some images we could use.

[matthiaskoenig]

I am finishing up the remaining issues of my SED-ML L1V4 implementation (such as surface plots based on the dimension reduction) then I can provide example images. I already have some examples for the 2D plots such as

• https://github.com/SED-ML/sedml-test-suite/blob/master/contributions/HARMONY%202021/sbmlsim/curve_types/curve_types_figure0.png
• https://github.com/SED-ML/sedml-test-suite/blob/master/contributions/HARMONY%202021/sbmlsim/curve_types_errors/curve_types_errors_figure0.png
• https://github.com/SED-ML/sedml-test-suite/blob/master/contributions/HARMONY%202021/sbmlsim/linetype/linetype_plot_0.png
• https://github.com/SED-ML/sedml-test-suite/blob/master/contributions/HARMONY%202021/sbmlsim/markertype/markertype_plot_0.png

[luciansmith]

This didn't end up going in, in the end. We can put them on the web page, perhaps, but I'm removing the L1v4 tag for now.