'constants' appear in reference json for v8

[scothis]

mapbox-gl-style-spec/reference/v8.json

Lines 53 to 56 in 66cc08c

	"constants": {
	"type": "constants",
	"doc": "An object of constants to be referenced in layers."
	},

mapbox-gl-style-spec/reference/v8.json

Lines 64 to 69 in 66cc08c

	"constants": {
	"*": {
	"type": "*",
	"doc": "A constant that will be replaced verbatim in the referencing place. This can be anything, including objects and arrays. All variable names must be prefixed with an `@` symbol."
	}
	},