dead link to code_of_conduct.md file in README.md
link corrected in this pr.
found using this tool I created:
@@ -289,7 +289,7 @@ yarn compile [...args]
### Contributor code of conduct
However you choose to contribute, please abide by our
-[code of conduct](https://github.com/closure-compiler/code_of_conduct.md) to
+[code of conduct](https://github.com/google/closure-compiler/blob/master/code_of_conduct.md) to
keep our community a healthy and welcoming place.
### Reporting a bug
