README adapted.

README.md

@@ -61,6 +61,8 @@ Put this content into the file (adapt the folder if you changed it above):
 ```
 #!/bin/bash
 
+export DISPLAY=:0.0
+
 while(true)
 do
         cd /home/pi/RhasspyVisualConversationTool/
@@ -73,6 +75,15 @@ done
 
 Make it runnable:  _chmod 775 /home/pi/Desktop/startConversationTool.sh_
 
+### Install xdotool to wake up the screen automatically
+When you address Rhasspy the screen will be turned on. For that feature the external application xdotool is utilized.
+
+You may still need to install it by executing
+
+```
+sudo apt install -y xdotool
+```
+
 ### Make the script autostart with the graphical user interface
 
 Create this file:  _/home/pi/.config/autostart/conversationTool.desktop_