Call for review: ARIA required owned element, add nested group role examples

Hey folks,

This PR adds an example showing that the group role can be used inside of
another group role, for the ARIA required owned elements role. This PR has
a one week review period, ending on December 21st. If you have any
comments, please leave a review before that time:

https://github.com/act-rules/act-rules.github.io/pull/1731

Kind regards,

-- 
*Wilco Fiers*
Axe-core & Axe-linter product owner - WCAG 3 Project Manager - Facilitator
ACT Task Force