add swing horizontal mode in mqtt climate docs (#37710)

* add swing horizontal mode in docs

* Update climate.mqtt.markdown

sorted alphabetically

source/_integrations/climate.mqtt.markdown

@@ -311,6 +311,27 @@ retain:
   required: false
   type: boolean
   default: false
+swing_horizontal_mode_command_template:
+  description: A template to render the value sent to the `swing_horizontal_mode_command_topic` with.
+  required: false
+  type: template
+swing_horizontal_mode_command_topic:
+  description: The MQTT topic to publish commands to change the swing horizontal mode.
+  required: false
+  type: string
+swing_horizontal_mode_state_template:
+  description: A template to render the value received on the `swing_horizontal_mode_state_topic` with.
+  required: false
+  type: template
+swing_horizontal_mode_state_topic:
+  description: The MQTT topic to subscribe for changes of the HVAC swing horizontal mode. If this is not set, the swing horizontal mode works in optimistic mode (see below).
+  required: false
+  type: string
+swing_horizontal_modes:
+  description: A list of supported swing horizontal modes.
+  required: false
+  default: ['on', 'off']
+  type: list  
 swing_mode_command_template:
   description: A template to render the value sent to the `swing_mode_command_topic` with.
   required: false
@@ -461,6 +482,9 @@ mqtt:
         - "off"
         - "cool"
         - "fan_only"
+      swing_horizontal_modes:
+        - "on"
+        - "off"
       swing_modes:
         - "on"
         - "off"
@@ -478,6 +502,7 @@ mqtt:
       mode_command_template: "{{ value if value=="off" else "on" }}"
       temperature_command_topic: "study/ac/temperature/set"
       fan_mode_command_topic: "study/ac/fan/set"
+      swing_horizontal_mode_command_topic: "study/ac/swingH/set"
       swing_mode_command_topic: "study/ac/swing/set"
       precision: 1.0
 ```