[thermostat] Add humidity support documentation (#5488)

Author: kbx81

content/components/climate/thermostat.md

@@ -161,8 +161,8 @@ Got all that? Great. Let's take a closer look at some configuration.
 The thermostat controller uses the sensor to determine whether it should heat or cool.
 
 - **sensor** (**Required**, [ID](#config-id)): The sensor that is used to measure the current temperature.
-- **humidity_sensor** (*Optional*, [ID](#config-id)): If specified, this sensor is used to measure the current humidity.
-  This is used for information only and does not influence temperature control.
+- **humidity_sensor** (*Optional*, [ID](#config-id)): The sensor that is used to measure the current humidity.
+  This may be used for humidity control; see [Humidity Control Actions](#humidity-control-actions).
 
 ### Heating and Cooling Actions
 
@@ -296,6 +296,20 @@ These should be used to control the fan only, if available.
 - **swing_both_action** (*Optional*, [Action](#config-action)): The action to call when the fan
   should oscillate in horizontal and vertical directions.
 
+### Humidity Control Actions
+
+These are triggered when the humidity control action is changed by the thermostat controller. It can trigger actions
+to activate humidification **or** dehumidification.
+
+- **humidity_control_dehumidify_action** (*Optional*, [Action](#config-action)): The action to call when
+  dehumidification is required.
+
+- **humidity_control_humidify_action** (*Optional*, [Action](#config-action)): The action to call when
+  humidification is required.
+
+- **humidity_control_off_action** (*Optional*, [Action](#config-action)): The action to call when
+  (de)humidification should stop. This action is **required** when either of the above actions are configured.
+
 ## Advanced Configuration/Behavior
 
 ### Set Point Options/Behavior
@@ -467,6 +481,9 @@ climate:
 
 ### Additional Actions/Behavior
 
+- **target_humidity_change_action** (*Optional*, [Action](#config-action)): The action to call when the
+  thermostat's target humidity is changed.
+
 - **target_temperature_change_action** (*Optional*, [Action](#config-action)): The action to call when the
   thermostat's target temperature(s) is/are changed.
 
@@ -544,6 +561,9 @@ the range of allowed temperature values in the thermostat component. See {{< doc
 - **heat_overrun** (*Optional*, float): The minimum temperature differential (heating beyond the set point)
   before calling the idle [action](#config-action). Defaults to 0.5 °C.
 
+- **humidity_hysteresis** (*Optional*, float): The maximum humidity differential (above/below the set point)
+  before calling the respective humidity control [action](#config-action). Defaults to 1%.
+
 > [!NOTE]
 >
 > - While this platform uses the term temperature everywhere, it can also be used to regulate other values.