Add "clientTimeout" topic to the documentation

Author: baxy

docs/WEBSOCKET-API.md

@@ -96,6 +96,7 @@ In the table bellow you can find the list of topics on which the `client` **must
 | Client Topic                                          | Server Topic                                      |
 |-------------------------------------------------------|---------------------------------------------------|
 | [invalidMessage](#invalidMessage)                     | none                                              |
+| [clientTimeout](#clientTimeout)                       | none                                              |
 | [requestRateLimitReached](#requestRateLimitReached)   | none                                              |
 | [ping](#ping)                                         | [pong](#pong)                                     |
 | [pongResponse](#pongResponse)                         | none                                              |
@@ -700,6 +701,27 @@ Example using wscat:
 
 ---
 
+#### clientTimeout
+If the server is not receiving any data from the client for more then 3 minutes, it will end the connection with the client.
+In this case it will send a message on this topic to let the client know the reason why it was diconnected.  
+
+This is not a message for which the server expects any response, so none should be sent back to the server!  
+
+```json
+{
+  "topic": "clientTimeout",
+  "payload": {
+    "success": false,
+    "data": [],
+    "dataLength": 0,
+    "warnings": ["No data received for more than 180 seconds, ending connection"],
+    "errors": []
+  }
+}
+```
+
+---
+
 #### requestRateLimitReached
 When a client is sending messages to the server with a high rate, it will throttle the requests from it send a warning message _"WebSocket request rate limit reached"_. 
 The client should listen for this messages on this topic to know when it happens.