[Feature request] providing C API

[hellodword]

It will be friendlier to other programming languages via FFI

• https://github.com/tensorflow/tensorflow/blob/0a124ecd3c704b7fff5ea2801c5a12dacfceb8c1/tensorflow/c/c_api.h
• https://github.com/microsoft/onnxruntime/blob/9479ba525b55dbbb4bf2bf4e18ce74c70ecf3171/include/onnxruntime/core/session/onnxruntime_c_api.h
• https://youtu.be/PVYdHDm0q6Y

[Vincent Nguyen]

Not planned, feel free to reopen if someone willing to wok on this.