[DOCS] Theengs Plug highlight and SEO improvements (#1730)

* [DOCS] Theengs Plug highlight

* Add alt content for images and description

docs/upload/advanced-configuration.md

@@ -67,7 +67,7 @@ To your environment definition.
 
 So as to create the MQTT username and password, you have to create a new user(recommended) into Home Assistant->Configuration->Users (available in admin mode) or use an existing username/pwd combination (not recommended). This user doesn't need to be an administrator.
 
-![](../img/OpenMQTTGateway-Configuration-Home-Assistant.png)
+![MQTT User](../img/OpenMQTTGateway-Configuration-Home-Assistant.png)
 
 ::: warning
 The max size of the username is 30 and 60 for the password.
@@ -77,4 +77,4 @@ OMG will use the auto discovery functionality of home assistant to create sensor
 
 The gateway device will be available into Configuration->Devices section of Home Assistant.
 
-![](../img/OpenMQTTGateway_Home_Assistant_MQTT_discovery.png)
+![MQTT Device settings](../img/OpenMQTTGateway_Home_Assistant_MQTT_discovery.png)