Updated readme to show badge on FEX

Author: callieEDU

README.md

@@ -5,6 +5,8 @@
 
 [![View on File Exchange](https://www.mathworks.com/matlabcentral/images/matlab-file-exchange.svg)](https://www.mathworks.com/matlabcentral/fileexchange/94635-transfer-function-analysis-of-dynamic-systems) or [![Open in MATLAB Online](https://www.mathworks.com/images/responsive/global/open-in-matlab-online.svg)](https://matlab.mathworks.com/open/github/v1?repo=MathWorks-Teaching-Resources/Transfer-Function-Analysis-of-Dynamic-Systems&project=TransferFunctions.prj)
 
+![MATLAB Versions Tested](https://img.shields.io/endpoint?url=https%3A%2F%2Fraw.githubusercontent.com%2FMathWorks-Teaching-Resources%2FTransfer-Function-Analysis-of-Dynamic-Systems%2Frelease%2FImages%2FTestedWith.json)
+
 **Curriculum Module**
 
 _Created with R2020b. Compatible with R2020b and later releases._