Add BrowserStack thanks

readme.md

@@ -63,6 +63,12 @@ Thank you to all our backers! 🙏 [[Become a backer](https://opencollective.com
 This project exists thanks to all the people who contribute.
 <img src="https://opencollective.com/git-history/contributors.svg?width=890&button=false" />
 
+### Thanks
+
+<a href="https://www.browserstack.com/"><img src="https://user-images.githubusercontent.com/1911623/66797775-4d651300-eee2-11e9-9072-ef1dc670af1d.png" width="250" height="auto"/></a>
+
+[BrowserStack](https://www.browserstack.com/) for letting open source projects use their services for free. Now I can test, debug and fix Safari issues from my Chrome running on Linux!
+
 ### Credits
 
 Based on these amazing projects: