Docs: Update samples in readme (#311)

* Remove MODBUS toc entry from readme

The example itself has been removed in
0644dca: 'Remove modbus-server to remove tokio 0.1 dependency.'

* Add event-client toc entry in readme

The example itself has been added in
8d2ba8d: 'Add a new event-client sample that subscribes to nothing but events'

README.md

@@ -69,4 +69,4 @@ The full list of samples:
 5. [`demo-server`](samples/demo-server) - an OPC UA server that is more complex than the simple server and can be used for compliance testing.
 6. [`mqtt-client`](samples/mqtt-client) - an OPC UA client that subscribes to some values and publishes them to an MQTT broker.
 7. [`web-client`](samples/web-client) - an OPC UA client that subscribes to some values and streams them over a websocket.
-8. [`modbus-server`](samples/modbus-server) - an OPC UA server that translates variables from MODBUS.
+8. [`event-client`](samples/event-client) - an OPC UA client that will connect to a server and subscribe to alarms / events.