Adds documentation for new integration flexit_bacnet (#29939)

* Add documentation for Flexit BACnet integration.

* Changed ha_release for flecit_bacnet integration

* Fix UI string markup

* Update source/_integrations/flexit_bacnet.markdown

* Changes ha_release

Co-authored-by: Joost Lekkerkerker <joostlek@outlook.com>

---------

Co-authored-by: Piotr Buliński <piotr@bulinski.no>
Co-authored-by: c0ffeeca7 <38767475+c0ffeeca7@users.noreply.github.com>
Co-authored-by: Joost Lekkerkerker <joostlek@outlook.com>

source/_integrations/flexit_bacnet.markdown

@@ -0,0 +1,27 @@
+---
+title: Flexit BACnet
+description: Instructions on how to integrate Flexit air handling unit into Home Assistant.
+ha_category:
+  - Climate
+ha_release: 2024.1
+ha_iot_class: Local Polling
+ha_domain: flexit_bacnet
+ha_platforms:
+  - climate
+ha_integration_type: integration
+---
+
+Integrates [Flexit](https://www.flexit.no/en/) Nordic series air handling unit into Home Assistant.
+
+## Prerequisites
+
+To configure the integration, you need to obtain the IP address and Device ID for the unit.
+
+1. Open the Flexit Go app on your mobile.
+2. On the main screen, select the **Find product** button.
+3. Select your device and select **Connect**.
+4. Enter the installer code (default: 1000) and select **Login**.
+5. Go to **More** > **Installer** > **Communication**  > **BACnet settings**.
+6. Note down the **IP address** and **Device ID**.
+
+{% include integrations/config_flow.md %}