Add exported onnx model 'model.onnx'

Hello!

*This pull request has been automatically generated from the [Sentence Transformers backend-export](https://huggingface.co/spaces/sentence-transformers/backend-export) Space.*

## Pull Request overview
* Add exported ONNX model `model.onnx`.

## Tip:
Consider testing this pull request before merging by loading the model from this PR with the `revision` argument:
```python
from sentence_transformers import SentenceTransformer

# TODO: Fill in the PR number
pr_number = 2
model = SentenceTransformer(
"Qwen/Qwen3-Embedding-0.6B",
revision=f"refs/pr/{pr_number}",
backend="onnx",
)

# Verify that everything works as expected
embeddings = model.encode(["The weather is lovely today.", "It's so sunny outside!", "He drove to the stadium."])
print(embeddings.shape)

similarities = model.similarity(embeddings, embeddings)
print(similarities)
```

.gitattributes

@@ -34,3 +34,4 @@ saved_model/**/* filter=lfs diff=lfs merge=lfs -text
 *.zst filter=lfs diff=lfs merge=lfs -text
 *tfevents* filter=lfs diff=lfs merge=lfs -text
 tokenizer.json filter=lfs diff=lfs merge=lfs -text
+onnx/model.onnx_data filter=lfs diff=lfs merge=lfs -text

onnx/model.onnx

@@ -0,0 +1,3 @@
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+oid sha256:ce458bd87656be8493863a4f0d25e5eaef8ad121c9df44e2301420202a3ec731
+size 1266212

onnx/model.onnx_data

@@ -0,0 +1,3 @@
+version https://git-lfs.github.com/spec/v1
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