Update CONTRIBUTING.md

CONTRIBUTING.md

@@ -9,8 +9,12 @@ Make sure to work in a branch to make it easier to create a new PR.
 **Important: Update the unit tests each time!**
 In fact I'd go out on a limb and say that you should use TDD for this project.
 
-## Step 3. Open a PR to review
+## Step 3. Run pre-commit
+Make sure to have pre-commit installed as git hook for this repository and use a virtualenviroment.
+This will run all the necessary tests and linters. Saving lots of time to the reviewers
+
+## Step 4. Open a PR to review
 Refer the Issue number in your PR
 
-## Step 4. Approval
+## Step 5. Approval
 Profit!