Added Steam Username property that should be set by user

lgsm/config-default/config-lgsm/vhserver/_default.cfg

@@ -114,6 +114,8 @@ appid="896660"
 branch=""
 # Master Server | https://docs.linuxgsm.com/steamcmd/steam-master-server
 steammaster="false"
+# Valheim requires steam login, I suggest starting steamcmd beforehand and use email authentification for steamguard. This way only steam username is required during updates, etc.
+steamuser="<UserName>"
 
 ## Stop Mode | https://docs.linuxgsm.com/features/stop-mode
 # 1: tmux kill