Pass through message topic to guest

[sjikob]

Currently only the message payload is passed through to the target component. It would be useful to additionally send the MQTT topic through. This would then allow the trigger to subscribe to wildcard topics, i.e. those containing + or # (which already works) but also provide some context to the component on the source of the message.

[suneetnangia]

That's a great suggestion, and I understand one would want to know what was the actual topic where the message arrived from in case of wildcard topic paths.