add screenshot for simple-scan

source/3/3.2/3.2.4/simple_scan.rst

@@ -12,6 +12,12 @@ Useage
 ------
 To use simple scan have your scanner turned on to start. To scan a page press the scan button. If you need to rotate a page to the left or the right you can easily use the arrows to the left or the right. If you are saving just one picture you can save it now as a jpeg. If you want to scan a multi-page document you can load the next page in the scanner now and the press scan and repeat this for the remaining pages. When you are finished press the save button and save the file as a pdf. 
 
+Screenshot
+----------
+ .. image:: simple_scan.png
+   :width: 80%
+
+
 How to Launch
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 To launch Simple Scan in the main menu under graphics click on the icon that looks like a glass sheet with a piece of paper and a beam of light across it like you would if you had the top up on a flatbed scanner looking down. Alternatively you can run simple-scan from the command line.