Update README.md

Add OpenIn Button to reademe

Author: dave-mw

README.md

@@ -2,6 +2,8 @@
 
 [![View histogramRangeSelector on File Exchange](https://www.mathworks.com/matlabcentral/images/matlab-file-exchange.svg)](https://www.mathworks.com/matlabcentral/fileexchange/95833-histogramrangeselector)
 
+[![Open in MATLAB Online](https://www.mathworks.com/images/responsive/global/open-in-matlab-online.svg)](https://matlab.mathworks.com/open/github/v1?repo=MATLAB-Graphics-and-App-Building/histogramRangeSelector)
+
 Version: 1.0
 
 ![histogramRangeSelector](/example_histogramRangeSelector.png)