Add link to action-groups.md

[TomashKhamlai]

Description

Provide a link to the corresponding section

Fixed Issues (if relevant)

1. Editorial

Contribution checklist

• Pull request has a meaningful description of its purpose
• All commits are accompanied by meaningful commit messages
• All new or changed code is covered with unit/verification tests (if applicable)
• All automated tests passed successfully (all builds on Travis CI are green)
• Changes to Framework doesn't have backward-incompatible changes for tests or have related Pull Request with fixes to tests

[coveralls]

Coverage decreased (-0.1%) to 51.881% when pulling 691b675 on TomashKhamlai:merging-link into 16d6880 on magento:develop.

[KevinBKozan]

@TomashKhamlai thank you for your contribution! I requested @dobooth's review as this is a doc only PR.