Add clang-format instructions for CLion

Author: rigtorp

03-Style.md

@@ -15,6 +15,7 @@ Whatever style guidelines you establish, be sure to implement a `.clang-format`
 
 Every IDE and many editors have support for clang-format built in or easily installable with an add-in.
 
+ * CLion: https://www.jetbrains.com/help/clion/clangformat-as-alternative-formatter.html
  * VSCode https://marketplace.visualstudio.com/items?itemName=xaver.clang-format
  * VisualStudio https://marketplace.visualstudio.com/items?itemName=LLVMExtensions.ClangFormat#review-details
  * Resharper++: https://www.jetbrains.com/help/resharper/2017.2/Using_Clang_Format.html