Add NDTensors.jl and ITensors.jl as a downstream test

[mtfishman]

Depends on ITensor/ITensors.jl#1617 to get downstream tests passing.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 83.07%. Comparing base (c95b95b) to head (4de577b).
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main      #34   +/-   ##
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  Coverage   83.07%   83.07%           
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  Files          14       14           
  Lines         254      254           
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  Hits          211      211           
  Misses         43       43           

Flag	Coverage Δ
docs	38.40% <ø> (ø)

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[mtfishman]

I had to remove the NDTensors.jl tests since it is a subdirectory package in the ITensors.jl repository, which isn't supported by the IntegrationTest.yml workflow (see ITensor/ITensorActions#17). I'll bring add it back once that issue is addressed in ITensorActions.