TODO list for the GPU implementation

[kmp5VT]

Right now because of how I have written the mixed hadamard contraction algorithm, GPU algorithms throw an error

[kmp5VT]

This issue is preventing GPU's to work across the board ITensor/ITensors.jl#1679. Working on a fix

[kmp5VT]

After merging the current PR #18 the running todo list here is:

1. Fix QR based algorithms for GPU. Currently QR is not supported by metal, I am not sure about the other libraries.
2. Check the other libraries and add Unit tests.
3. Benchmark the GPU algorithms on NVIDIA

[kmp5VT]

With #19, I fixed the issues with ITensor Networks.