[mirotalksfu] - update readme

README.md

@@ -16,7 +16,7 @@ Open the app with the following **supported browsers** and many more.
 
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-[![mirotalksfu](public/images/mirotalksfu-header.png)](https://sfu.mirotalk.org/)
+[![mirotalksfu](public/images/mirotalksfu-header.gif)](https://sfu.mirotalk.org/)
 
 ## Features