Merge branch '3rd-party-parallel-tools' into 'master'

Add 3rd party parallel tools section to docs

See merge request gitlab-org/gitlab-ce!30434

doc/ci/examples/README.md

@@ -37,6 +37,7 @@ The following table lists examples with step-by-step tutorials that are containe
 | Python on Heroku            | [Test and deploy a Python application with GitLab CI/CD](test-and-deploy-python-application-to-heroku.md).                 |
 | Ruby on Heroku              | [Test and deploy a Ruby application with GitLab CI/CD](test-and-deploy-ruby-application-to-heroku.md).                     |
 | Scala on Heroku             | [Test and deploy a Scala application to Heroku](test-scala-application.md).                                                |
+| Parallel testing Ruby & JS  | [GitLab CI parallel jobs testing for Ruby & JavaScript projects](https://docs.knapsackpro.com/2019/how-to-run-parallel-jobs-for-rspec-tests-on-gitlab-ci-pipeline-and-speed-up-ruby-javascript-testing). |
 
 ### Contributing examples
 

doc/ci/yaml/README.md

@@ -1779,6 +1779,10 @@ test:
   parallel: 5
 ```
 
+TIP: **Tip:**
+Parallelize tests suites across parallel jobs.
+Different languages have different tools to facilitate this.
+
 ### `trigger` **(PREMIUM)**
 
 > [Introduced](https://gitlab.com/gitlab-org/gitlab-ee/issues/8997) in [GitLab Premium](https://about.gitlab.com/pricing/) 11.8.