Add instructions to check translation changes (publiclab#10027)

Author: imajit

db/seeds.rb

@@ -92,5 +92,6 @@
                   "body"=>"Welcome to the plots2 application!
                   This message is displayed only to developers running the code in a development environment (normally it's the front page content!).
                   To use a lot of the features on this site, even locally, you'll have to <a href='/login'>log in</a>. Default username and password are
-                  username: admin, moderator, or user and password: password. If you run into trouble, please reach out at https://publiclab.org/chat or in our getting started issue at https://github.com/publiclab/plots2/issues/3840",
+                  username: admin, moderator, or user and password: password. If you run into trouble, please reach out at https://publiclab.org/chat or in our getting started issue at https://github.com/publiclab/plots2/issues/3840 .
+                  To test UI changes related to 'Translation-System' please login and 'Switch on Translation' from the drop-down menu visible on hoverig over profile picture in top navigation bar.",
                   "teaser"=>"", "log"=>"", "format"=>1