Update README.md

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README.md

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 # **Simscape Tutorial Exercises**
 Copyright 2011-2020 The MathWorks(TM), Inc.
 
+[![View Simscape Tutorial Exercises on File Exchange](https://www.mathworks.com/matlabcentral/images/matlab-file-exchange.svg)](https://www.mathworks.com/matlabcentral/fileexchange/17238-simscape-tutorial-exercises)
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 These models can be used as tutorial exercises.  
 In the Solution directory for each example, you can find the final model and 
 intermediate steps for each model.  These examples show many basic systems