Secondary colors for polygon outlines in `viz`

[kylebarron]

We should infer some default colors for polygon outlines when rendering data through viz. The existing primary colors are here, which are randomly chosen:

lonboard/lonboard/_viz.py

Lines 72 to 86 in 2bed40c

	# From mbview
	# https://github.com/mapbox/mbview/blob/e64bd86cfe4a63e6af4ea1d310bd49be4f162a43/views/vector.ejs#L75-L87
	COLORS = [
	"#FC49A3", # pink
	"#CC66FF", # purple-ish
	"#66CCFF", # sky blue
	"#66FFCC", # teal
	"#00FF00", # lime green
	"#FFCC66", # light orange
	"#FF6666", # salmon
	"#FF0000", # red
	"#FF8000", # orange
	"#FFFF66", # yellow
	"#00FFFF", # turquoise
	]

This is a separate issue separated from #330

[kylebarron]

cc @batpad

[kylebarron]

For now I'm using a black outline

[kylebarron]

I think defaulting to black is probably best