Update submissions.json

```
hf jobs uv run \
--flavor "a10g-large" \
--secrets HF_TOKEN \
--with "lighteval[vllm]" \
--with 'vllm<=0.10' \
lighteval vllm "model_name=jweston/SmolLM3-Custom-SFT" "lighteval|gsm8k|0|0" --push-to-hub --results-org "jweston"
```

submissions.json

@@ -6,6 +6,13 @@
             "chapter": "1",
             "submission_date": "2025-09-02",
             "results-dataset": "smol-course/details_HuggingFaceTB__SmolLM3-3B_private"
-        }
+        },
+        {
+            "username": "jweston",
+            "model_name": "SmolLM3-Custom-SFT",
+            "chapter": "1",
+            "submission_date": "2025-09-18",
+            "results-dataset": "jweston/details_jweston__SmolLM3-Custom-SFT_private"
+        },
     ]
 }