Add Contributing Section to README

Adds Contributing section to readme.

README.md

@@ -125,3 +125,7 @@ Before getting into changing the code, try to use the following structure (feel
 - `tasks` - Those are the parts of the code that talk to the external world: it has the tasks that are triggered by external containers. They can depend on `helpers`, `models` and `services`, but NEVER depend on another task (except to schedule them). If some code is common to two tasks, try to put it in a `service` or somewhere else.
 
 You will also notice some usage of the package https://github.com/codecov/shared for various things. The logic that is there is used by both here and `codecov/api` codebase. So feel free to make changes there, but dont do anything that will break compatibility too hard.
+
+## Contributing
+
+This repository, like all of Codecov's repositories, strives to follow our general [Contributing guidlines](https://github.com/codecov/contributing). If you're considering making a contribution to this repository, we encourage review of our Contributing guidelines first.