Update README.md

Author: govert

SpecialTopics/IntelliSenseForVBAFunctions/README.md

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 ![IntelliSense in action](https://user-images.githubusercontent.com/414659/100517124-37bbb700-3191-11eb-8c3b-8125322a6f63.gif)
 
 
+[![Excel-DNA IntelliSense for VBA Functions](http://img.youtube.com/vi/-BIOzl1igXU/0.jpg)](http://www.youtube.com/watch?v=-BIOzl1igXU "Excel-DNA IntelliSense for VBA Functions")
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 ## Background
 
 When you edit a formula on a worksheet, Excel has two mechanisms to assist you in entering the right function call information.