message: Improve CONTRIBUTING.md
  Summary:
  Made it easier to reach the .clang-format file by adding a link to it.
  Closes
diff: @@ -42,7 +42,7 @@ Our only hard-and-fast coding style rules are:
  * 2 spaces for indentation rather than tabs
  * 80 character line length
  -In general, if you use our .clang-format file in the root of this repo, no one
  +In general, if you use our [.clang-format file](https://github.com/facebook/redex/blob/master/.clang-format), no one
  will complain.
  ## License
  