Upload model.onnx

Adding the ONNX version of the model from this repo.

created with this command:

python3 -m transformers.onnx --model='sentence-transformers/all-MiniLM-L6-v2'

model.onnx

@@ -0,0 +1,3 @@
+version https://git-lfs.github.com/spec/v1
+oid sha256:1318359ed02ed53e8af09bbf699c8faca4a83a44f3af81d1e138eca0162a6853
+size 90979430