Add presentation performance graph to docs

[kylebarron]

[sam-capellaspace]

This is definitely an impressive plot showing lonboard's rendering performance. Can you modify the plot so that the y-axis is in logarithmic scale? Or at least include a log scale plot alongside this one?

[kylebarron]

The graphs were originally made in #597

Part of the idea with the graph was to say that all three libraries scale linearly, but that Lonboard is much more efficient. I felt that the linear y scale was appropriate for that, but I could make a log scale version too