v0.2.4 more ops; support for more ONNX data types.

[janpfeifer]

• Added support to other ONNX dtypes that requires conversion during reading.
  Also added conversion when saving values back to the ONNX proto.
• Updated dependencies to GoMLX.
• Added onnxtests.py to help test/explore individual ONNX ops using ONNXRuntime.
• New ops: DequantizeLinear, DynamicQuantizeLinear.

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This discussion was created from the release v0.2.4 more ops; support for more ONNX data types..