add config.json (required for HF download-count tracking)

config.json

@@ -0,0 +1,13 @@
+{
+  "model_type": "speednet",
+  "architectures": ["SpeedNet"],
+  "task": "ego-speed-estimation",
+  "input": "optical_flow_128x72_plus_rgb_context",
+  "output": "speed_mps",
+  "hidden_size": 192,
+  "flow_cnn_blocks": 4,
+  "context_cnn_blocks": 3,
+  "gru_layers": 2,
+  "sample_rate_hz": "variable (short: 16-frame, streaming: any)",
+  "framework": "pytorch"
+}