Use inds_network in PEPS constructor

[mtfishman]

The PEPS constructor can be simplified with the inds_network function, like is shown here:

ITensorNetworkAD.jl/examples/ITensorNetworks/peps.jl

Lines 7 to 25 in c178a13

	function peps_tensor(; linkdim, sitedim)
	# left, right, top, bottom, site
	return randn(linkdim, linkdim, linkdim, linkdim, sitedim)
	end
	N = (3, 4)
	ndims = length(N)
	site_inds = siteinds("S=1/2", N...)
	link_space = 2
	inds_net = inds_network(site_inds; linkdims=link_space)
	A = peps_tensor(; linkdim=link_space, sitedim=dim(first(site_inds)))
	ψ = itensor.((A,), inds_net)
	# Project periodic boundary indices
	# onto the 1 state
	state = 1
	ψ = project_boundary(ψ, state)

Cross reference: #10 (comment)_