Add SvgHandler in Draw.io wiki guide

SvgHandler is needed to show SVG output from Draw.io in webbrowser.

Guides/wiki.md

@@ -115,6 +115,8 @@ _todo_
 cd /var/www/mediawiki/extensions/
 
 sudo git clone https://github.com/mgeb/mediawiki-drawio-editor DrawioEditor
+
+sudo git clone https://github.com/p12tic/NativeSvgHandler.git
 ```
 
 **Fix SVG upload** : add `http://www.w3.org/1999/xhtml` in `/var/www/mediawiki/includes/upload/UploadBase.php`.