Add guideline for building nuget package and example usage

[chilo-ms]

Add guideline for building nuget package and providing C# example usage for TensorRT plugin EP.

[edgchen1]

are we trying to create a nuget package that will be published, or just showing an example of how to create a nuget package?

if it's the former, would we want to support having both x64 and arm64 builds in one package?

[chilo-ms]

We are providing an example of how to create a nuget package at this moment.

We or others can update this setup.bat once there is a request for publishing a TensorRT plugin ep nuget package.

[edgchen1]

hm, if all we want to do is provide an example, why not refer to this one instead?
https://github.com/microsoft/onnxruntime-inference-examples/tree/main/plugin_execution_providers/basic/csharp

[chilo-ms]

Eventually, the TensorRT plugin ep nuget package will be published either by us or Nvidia.
Let me add the support for x64 and arm64 builds.

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