[WIP] added erf support

[brightening-eyes]

hi,
the first operator that I would like to contribute is erf
pytorch by itself breaks gelu when the model is converted to onnx by torch.onnx.export into peaces
for loongarch etc, I don't know about their instruction sets, and how I can implement it.
I will be adding more and more.
with this, wav2vec2, etc can be easily exported to ncnn from onnx
if there is anything I should add/fix, let me know and I will update this pull until everything works out.

[tencent-adm]

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1 out of 2 committers have signed the CLA.

✅ brightening-eyes
❌ Amir Ramezani

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