[QA] Update API

Author: jferdelyi

README.md

@@ -63,12 +63,18 @@ The picture represent the demo project:
 
 ``` gdscript
 # Initialize the client
-# @param id string to use as the client id.
+# @param id string to use as the client id
 # @param host the broker address
 # @param port the broker port
 # @return the reason code, if something wrong happen. 0 = OK (see https://docs.oasis-open.org/mqtt/mqtt/v5.0/os/mqtt-v5.0-os.html#_Toc3901031)
 initialise(id: String, host: String, port: String) -> int
 
+# Set username & password
+# @param p_username username
+# @param p_pasword password
+# @return the reason code, if something wrong happen. 0 = OK (see https://docs.oasis-open.org/mqtt/mqtt/v5.0/os/mqtt-v5.0-os.html#_Toc3901031)
+username_pw_set(username: String, password: String) -> int
+
 # Return true if connected 
 # @return true if connected 
 is_connected_to_broker() -> bool