Update README.md

Author: mtfishman

README.md

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+| :warning: WARNING          |
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+| This package is a work in progress! There is minimal documentation, and you are expected to understand infinite MPS methods before using the code. Please first read references on tangent space methods for infinite MPS and be sure to understand the mixed canonical form of MPS (https://arxiv.org/abs/1701.07035, https://arxiv.org/abs/1802.07197, https://arxiv.org/abs/1810.07006), and also read through the code and examples to understand the code design, philosophy, and supported infinite MPS operations. This package is *not* as feature-rich and field-tested as the MPS/DMRG implementation in ITensors.jl. The VUMPS algorithm is much newer than the DMRG algorithm, and the convergence properties and best practices of the algorithm are not as well understood as the DMRG algorithm. You are expected to work out best practices on your own, tune parameters, and feel free to share your experiences through the issues or the ITensor Discourse forum (https://itensor.discourse.group/). If/when you come across issues, please try to read the code and debug the issue yourself, and raise issues and/or make pull requests fixing issues through Github (https://github.com/ITensor/ITensorInfiniteMPS.jl/issues, https://github.com/ITensor/ITensorInfiniteMPS.jl/pulls). |
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 # ITensorInfiniteMPS
 
 ## Introduction