Merge pull request #237 from groosg/master

Add Haskell Dockerfile Linter

README.md

@@ -581,6 +581,7 @@ Only main chapters:
 &nbsp;&nbsp;:small_orange_diamond: <a href="http://sandbox.onlinephpfunctions.com/"><b>PHP Sandbox</b></a> - test your PHP code with this code tester.<br>
 &nbsp;&nbsp;:small_orange_diamond: <a href="https://www.repl.it/"><b>Repl.it</b></a> - an instant IDE to learn, build, collaborate, and host all in one place.<br>
 &nbsp;&nbsp;:small_orange_diamond: <a href="http://www.vclfiddle.net/"><b>vclFiddle</b></a> - is an online tool for experimenting with the Varnish Cache VCL.<br>
+&nbsp;&nbsp;:small_orange_diamond: <a href="https://github.com/hadolint/hadolint"><b>Haskell Dockerfile Linter</b></a> - a smarter Dockerfile linter that helps you build best practice Docker images.<br>
 </p>
 
 ##### :black_small_square: Performance