Docs: add info to turn on github actions (#2264)

* add info to turn on github actions

* add missing image

* add when pushing

* reduce picture size

* mention editing actions on your fork instead

docs/contributing.md

@@ -1,9 +1,11 @@
 # Contributing
 Contributions are welcome. We have a few requests of any new contributors.
 
+* Follow styling as designated in our [styling documentation](/docs/style.md).
 * Ensure that all changes which affect logic are covered by unit tests. 
 * Do not introduce any unit test failures/regressions.
-* Follow styling as designated in our [styling documentation](/docs/style.md).
+* Turn on automated github actions in your fork to have github run all the unit tests after pushing. See example below:
+![Github actions example](./img/github-actions-example.png)
 
 Otherwise, we tend to judge code on a case to case basis.