version dependency

[mengniwang95]

I wonder if there is version dependency between onnxruntime-extensions, onnx and onnxruntime?
If so, could you offer the version mapping?

[wenbingl]

@mengniwang95
as it states in requirements.txt,

onnx>=1.9.0
onnxruntime>=1.6.0

the API is backward compatible, so it doesn't have to be N:M version mapping.