Document optional MQTT cover options (#17971)

* Document optional MQTT cover options

* Fix missing quote

Co-authored-by: Franck Nijhof <git@frenck.dev>

Co-authored-by: Franck Nijhof <git@frenck.dev>

source/_integrations/cover.mqtt.markdown

@@ -422,6 +422,45 @@ cover:
 
 {% endraw %}
 
+### Configuration for disabling cover commands
+
+The example below shows a configuration for a cover that does not have a close command.
+Setting `payload_close` empty or to `null` disables the close command and will not show the close button.
+
+{% raw %}
+
+```yaml
+# Example configuration.yaml entry
+cover:
+  - platform: mqtt
+    payload_open: "on"
+    payload_close: 
+    payload_stop: "on"
+```
+
+{% endraw %}
+The following commands can be disabled: `open`, `close`, `stop` by overriding their payloads: `payload_open`, `payload_close`, `payload_stop`
+
+For auto discovery message the payload needs to be set to `null`, example for cover without close command:
+{% raw %}
+
+```json
+{
+  "cover": [
+    {
+      "platform": "mqtt",
+      "payload_open": "on",
+      "payload_close": null,
+      "payload_stop": "on"
+    }
+  ]
+}
+```
+
+{% endraw %}
+
+### Testing your configuration
+
 To test, you can use the command line tool `mosquitto_pub` shipped with `mosquitto` or the `mosquitto-clients` package to send MQTT messages. This allows you to operate your cover manually:
 
 ```bash