Add Adax heaters (#17950)

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

source/_integrations/adax.markdown

@@ -0,0 +1,26 @@
+---
+title: Adax
+description: Instructions on how to integrate Adax heater into Home Assistant.
+ha_category:
+  - Climate
+ha_release: 2021.8
+ha_iot_class: Cloud Polling
+ha_codeowners:
+  - '@danielhiversen'
+ha_domain: adax
+ha_config_flow: true
+ha_platforms:
+  - climate
+---
+
+Integrates Adax heater into Home Assistant.
+
+You'll need the Account ID (which can be found in the Adax Wifi app, pressing 'Account'). You will also need a credential, which you can create in the Adax app:
+
+1. Navigate to Account Tab,
+2. Select “Remote user client API”
+3. Select “Add Credential”
+4. Give some name to the created credential and copy the generated password.
+
+
+{% include integrations/config_flow.md %}