Add definitions of delta and Ising networks

[mtfishman]

No description provided.

[codecov]

Codecov Report

❌ Patch coverage is 91.66667% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 64.03%. Comparing base (255d482) to head (95ec80b).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
src/TensorNetworkGenerators/ising_network.jl	89.65%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #18      +/-   ##
==========================================
+ Coverage   58.88%   64.03%   +5.15%     
==========================================
  Files           8       11       +3     
  Lines         574      609      +35     
==========================================
+ Hits          338      390      +52     
+ Misses        236      219      -17     

Flag	Coverage Δ
docs	0.00% <0.00%> (ø)

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