update documentation (and function to actually allow for a mixture of Gaussians)

[hematthi]

EchelleCCFs.jl/src/mask_shapes/gaussian_mixture.jl

Lines 48 to 54 in a639217

	""" `GaussianMixtureCCFMask( inst ; scale_factor )`
	For now just makes a single Gaussian, so for testing purposes only.
	"""
	function GaussianMixtureCCFMask(inst::AbstractInstrument; σ_scale_factor::Real = 1, truncation_Δv::Real = default_gaussian_mixture_ccf_truncation_Δv )
	σ = σ_scale_factor * default_ccf_mask_v_width(inst)
	GaussianMixtureCCFMask([1.0], [σ],truncation_Δv,v_offset=[0.])
	end