docs: enhance freqUI documentation page structure

Author: xmatthias

docs/freq-ui.md

@@ -70,7 +70,16 @@ Things you can change (among others):
 ![FreqUI - Settings view](assets/frequi-settings-dark.png#only-dark)
 ![FreqUI - Settings view](assets/frequi-settings-light.png#only-light)
 
-## Backtesting
+## Webserver mode
+
+when freqtrade is started in [webserver mode](utils.md#webserver-mode) (freqtrade started with `freqtrade webserver`), the webserver will start in a special mode allowing for additional features, for example:
+
+* Downloading data
+* Testing pairlists
+* [Backtesting strategies](#backtesting)
+* ... to be expanded
+
+### Backtesting
 
 When freqtrade is started in [webserver mode](utils.md#webserver-mode) (freqtrade started with `freqtrade webserver`), the backtesting view becomes available.
 This view allows you to backtest strategies and visualize the results.