FB_INPUT_BINARYSENSOR_MQTT: supporting MQTT discovery

[MichielVanwelsenaere]

Pull Request Checklist

Check if the tasks below are relevant for your PR, to mark an item as completed use [X].

• [x] I followed the CONTRIBUTING.md
• [x] Updated the PLCOpen XML export file (only relevant on code change).
• [x] Updated the CoDeSys V3 export file (only relevant on code change).
• [x] Updated or created any relevant documentation.

Proposed Changes

• Supporting MQTT discovery on FB_INPUT_BINARYSENSOR_MQTT