Improved: Manual: username+pw for demo login (#4072)

* added: username+pw for demo login

* fix white spaces

docs/en/index.md

@@ -33,6 +33,11 @@ This documentation is split into different sections:
 
 The official demo of FreshRSS is available under [https://demo.freshrss.org/](https://demo.freshrss.org/).
 
+Login credentials:
+
+* Username: demo
+* Password: demodemo
+
 Another chance to try out, but not official supported by FreshRSS: The application is listed on Softaculous [https://www.softaculous.com/apps/rss/FreshRSS](https://www.softaculous.com/apps/rss/FreshRSS).
 
 ## Licence