Apply the model card standard

README.md

@@ -17,17 +17,22 @@ Upstream model: [RFDetr](https://github.com/roboflow/rf-detr)
 | Path | Backend | Precision |
 | --- | --- | --- |
 | `coreml/rfdetr_keypoint_preview_coreml_fp16.pte` | coreml | fp16 |
-| `mlx/rfdetr_keypoint_preview_mlx_fp32.pte` | mlx | fp32 |
 | `xnnpack/rfdetr_keypoint_preview_xnnpack_fp32.pte` | xnnpack | fp32 |
 
+## Unshipped backends
+
+A backend directory carrying a `NOTES.md` and no `.pte` was exported and
+not published. Its note records why.
+
+- `mlx` ([why](https://huggingface.co/software-mansion/react-native-executorch-rfdetr-keypoint/blob/main/mlx/NOTES.md))
+
 ## Repository structure
 
 ```
 config.json                                       37 B
 coreml/config.json                                1.1 kB
 coreml/rfdetr_keypoint_preview_coreml_fp16.pte    71.5 MB
-mlx/config.json                                   1.1 kB
-mlx/rfdetr_keypoint_preview_mlx_fp32.pte          139 MB
+mlx/NOTES.md                                      1.4 kB
 xnnpack/config.json                               1.1 kB
 xnnpack/rfdetr_keypoint_preview_xnnpack_fp32.pte  139 MB
 ```