feat: find best embedding matches

[thewh1teagle]

Resolve #1096

[csukuangfj]

Thanks! Left some minor comments. Otherwise, it looks good to me.

[csukuangfj]

Suggested change

	SherpaOnnxSpeakerEmbeddingManagerSpeakerMatch *matches;
	const SherpaOnnxSpeakerEmbeddingManagerSpeakerMatch *matches;

[thewh1teagle]

When using const there I get the following compile error

/Users/user/Documents/sherpa-rs/sys/sherpa-onnx/sherpa-onnx/c-api/c-api.cc:1275:30: error: read-only variable is not assignable
    result->matches[i].score = matches[i].score;
    ~~~~~~~~~~~~~~~~~~~~~~~~ ^
/Users/user/Documents/sherpa-rs/sys/sherpa-onnx/sherpa-onnx/c-api/c-api.cc:1281:29: error: read-only variable is not assignable
    result->matches[i].name = name;
    ~~~~~~~~~~~~~~~~~~~~~~~ ^

I think we'll need to use internal non const in the function and case it to const before return

[thewh1teagle]

Fixed in 7d2341d

[csukuangfj]

Thank you for your first-time contribution!