Add external server return format to ReadMe

Signed-off-by: Test Account <azgeorgi@noreply.localhost>

README.md

@@ -57,4 +57,14 @@ ALVINN can use an external object detection server instead of the built in model
 | --- | --- | --- |
 | `name` | identifier for external server | *none* |
 | `address` | ip or url of external server | *none* |
-| `port` | port to access on external server | 9001 |
+| `port` | port to access on external server | 9001 |
+
+The external server's response must be json with a `detections` key that contains an array of the detected structure labels, bounding box data, and confidence values.
+```
+{
+  "detections": [
+    {"top": 0.1, "left": 0.1, "bottom": 0.9, "right": 0.9, "label": "dog", "confidence": 90.0 }
+    ...
+  ],
+}
+```