Adds info about supported platforms to flexit_bacnet (#30941)

* Adds info about supported platforms to flexit_bacnet

# Conflicts:
#	source/_integrations/flexit_bacnet.markdown

* Adds docs for binary sensor

source/_integrations/flexit_bacnet.markdown

@@ -28,4 +28,36 @@ To configure the integration, you need to obtain the IP address and Device ID fo
 5. Go to **More** > **Installer** > **Communication**  > **BACnet settings**.
 6. Note down the **IP address** and **Device ID**.
 
+## Platforms
+
+This integration supports the following platforms.
+
+### Climate
+
+The integration adds an entity for climate with controls for preset ventilation modes and fan mode. It also has state for temperatures.
+
+### Sensor
+
+The integration adds entities for sensors with different readings from the device. There is currently support for the following sensors:
+
+ - Outside air temperature
+ - Supply air temperature 
+ - Exhaust air temperature
+ - Extract air temperature
+ - Room temperature
+ - Fireplace ventilation remaining duration
+ - Rapid ventilation remaining duration
+ - Supply air fan control signal
+ - Supply air fan
+ - Exhaust air fan control signal
+ - Exhaust air fan
+ - Electric heater power
+ - Air filter operating time
+ - Heat exchanger efficiency
+ - Heat exchanger speed
+
+### Binary sensor
+
+The integration adds an entity for a binary sensor called _Air filter polluted_ which tells if it's time to change the filters in the unit.
+
 {% include integrations/config_flow.md %}