Feature/extend development guide to start client in other languages (#4881)

* Extend start client guide

DEVELOPMENT.md

@@ -30,7 +30,13 @@ Run `npm run start:server`
 
 ### Start Client
 
-Run `npm run start:client` and open https://localhost:4200/en in your browser
+#### English (Default)
+
+Run `npm run start:client` and open https://localhost:4200/en in your browser.
+
+#### Other Languages
+
+To start the client in a different language, such as German (`de`), adapt the `start:client` script in the `package.json` file by changing `--configuration=development-en` to `--configuration=development-de`. Then, run `npm run start:client` and open https://localhost:4200/de in your browser.
 
 ### Start _Storybook_