Add new Tasmota value to Home Assistan via MQTT config topic message

== How to transfer a new Tasmota value from your Tasmota Script to Home Assistant ==

You can use MQTT Discovery in HA to add sensors and other entities that are not discovered through Tasmota integration and associate them with an already discovered device.

More infos:
https://www.home-assistant.io/integrations/sensor.mqtt/#configuration-variables
https://github.com/home-assistant/core/blob/dev/homeassistant/components/mqtt/abbreviations.py
https://tasmota.github.io/docs/Home-Assistant/#supplemental-custom-discovery-message

HOWTO
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1) add a new line of code inside your script
   e.g. =>publish stat/%topic%/script/consday %2(dcon[day])%
   e.g. in this script section:

>S
if (secs%60==0)
{
  =>publish stat/%topic%/script/consday %dcon[day]%
}

  See example script ottelo.jimdofree.com/stromz%C3%A4hler-auslesen-tasmota/#SkriptDownload.

2) Install and start MQTT Explorer in HA
3) Look for your new MQTT sensor inside MQTT Explorer e.g. stat/%topic%/script/consday = xxx
4) Publish a new config topic to Home Assistant with MQTT Explorer. Home Assistant will then automatically add the sensor to the already published device.
5) Click on topic "homeassistant/sensor". On right side click on "homeassistant/sensor" below "Publish". Change the topic address to e.g. "homeassistant/sensor/mt175/consday/config"
6) Then paste the following JSON code into the field and activate the retain flag. Change or add mqtt config variables if needed (use abbreviations to keep everything short, see url above). A02xxxxAFAD3 is the MAC of Tasmota and tasmota_1AFAD3 the topic + last part of MAC. Change it!

Example Yieldday of Smartmeter MT175 (yieldday calculated inside Tasmota script and saved into array dprod[day]):
{
  "name": "Smartmeter Day Consumption",
  "uniq_id": "mt175_dayconsumption",
  "dev_cla": "energy",
  "stat_t": "stat/tasmota_1AFAD3/script/consday",
  "unit_of_meas": "kWh",
  "dev": {
    "connections": [
      [
        "mac",
        "A02xxxxAFAD3"
      ]
    ]
  }
}

7) Press on Publish


Other example:
=>publish stat/%topic%/RESULT {"script":{"power2":%power2%}}
Config topic: homeassistant/sensor/mt175/config
{
  "name": "Stromzähler Leistung (gefiltert)",
  "uniq_id": "mt175_mt175_power2",
  "dev_cla": "power",
  "stat_t": "stat/tasmota_1AFAD3/RESULT",
  "unit_of_meas": "W",
  "val_tpl": "{{value_json.script.power2}}",
  "sug_dsp_prc": "0",
  "dev": {
    "connections": [
      [
        "mac",
        "A02xxxxAFAD3"
      ]
    ]
  }
}