Determine resolution of P.E. peaks in SiPM gaussian mixture

[fhagemann]

Currently, the resolution of the P.E. peaks is calculated as

LegendSpecFits.jl/src/sipmfit.jl

Lines 109 to 111 in 6eece2d

	get_pe_res = pe -> let sel = in.(μ, (-Δpe_peak_assignment..Δpe_peak_assignment) .+ pe)
	sqrt(dot(view(σ, sel).^2, view(w, sel).^2))
	end

This should be updated.