Update ReadMe

wikipedia_to_opale/README.md

@@ -58,6 +58,8 @@ Generating .hdoc of a Wikipedia article with a local file
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 1 - Copy the content of the Wikipedia article you want to convert in the directory named “input” and in a file called “source.xml".
+    Display the source code of the wikipedia page, copy it and paste it in the new file source.xml
+    Make sure to copy/paste the source code and not save it directly as a file.
     
 2 - Run the comand corresponding to your OS