Add .git-blame-ignore-revs to CONTRIBUTING.md

CONTRIBUTING.md

@@ -92,6 +92,12 @@ The project uses [scalafmt](https://scalameta.org/scalafmt/) to ensure code qual
 every PR. If you would like to check for any potential code style problems locally you can run `sbt checkCodeStyle`
 and if you want to apply the code style then you can run `sbt applyCodeStyle`.
 
+### Ignoring formatting commits in git blame
+
+Throughout the history of the codebase various formatting commits have been applied as the scalafmt style has evolved over time, if desired
+one can setup git blame to ignore these commits. The hashes for these specific are stored in [this file](.git-blame-ignore-revs) so to configure
+git blame to ignore these commits you can execute the following.
+
 ## How To Enforce These Guidelines?
 
 1. [CI](https://github.com/apache/incubator-pekko-management/actions) automatically merges the code, builds it, runs the tests and sets Pull Request status accordingly of results in GitHub.