Define filling for curves with type point

[jonrkarr]

(Edited because I see that fill isn't defined -- "The Fill of a Style has no meaning and, if present, will be ignored.").

I think this requires more information to capture how curves can be filled.

For reference, here's the documentation for Plotly's fill attribute

Type: enumerated , one of ( "none" | "tozeroy" | "tozerox" | "tonexty" | "tonextx" | "toself" | "tonext" )

Sets the area to fill with a solid color. Defaults to "none" unless this trace is stacked, then it gets "tonexty" ("tonextx") if orientation is "v" ("h") Use with fillcolor if not "none". "tozerox" and "tozeroy" fill to x=0 and y=0 respectively. "tonextx" and "tonexty" fill between the endpoints of this trace and the endpoints of the trace before it, connecting those endpoints with straight lines (to make a stacked area graph); if there is no trace before it, they behave like "tozerox" and "tozeroy". "toself" connects the endpoints of the trace (or each segment of the trace if it has gaps) into a closed shape. "tonext" fills the space between two traces if one completely encloses the other (eg consecutive contour lines), and behaves like "toself" if there is no trace before it. "tonext" should not be used if one trace does not enclose the other. Traces in a stackgroup will only fill to (or be filled to) other traces in the same group. With multiple stackgroups or some traces stacked and some not, if fill-linked traces are not already consecutive, the later ones will be pushed down in the drawing order.