add ONNX support for swin transformer
Author: bibhabasumohapatra
Pull request: yes

# What does this PR do?

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Addresses #16308


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it was already addressed in PR #18171 (but was mistakenly closed by me, Sorry for the repeat PR)
@lewtun @ChainYo 

Comments:
_The documentation is not available anymore as the PR was closed or merged._

Thanks 
Great start on Huggingface, hope to keep contributing more.