[OOS - Release Docs] Docs for configuring a Competency Rule Profile #647

This issue adds user-facing documentation for configuring a Competency Rule Profile.

Documentation should explain what a Competency Rule Profile is, when to use one versus configuring a rule directly on a criterion, how it is scoped and selected at the organization, course, or taxonomy level, and how precedence works when more than one level applies. Documentation should follow the same process used for the previous taxonomy editing work, with docs added to the Open edX documentation repository.

Release notes are not expected to be created as part of this ticket. Axim is experimenting with generating release notes separately, and the team may share those for review if needed.

Documentation Location:
Documentation should be added to the Open edX documentation repository:
https://github.com/openedx/docs.openedx.org

Outstanding/Needs Confirmation:
Confirm the exact documentation page or section where Competency Rule Profile content should be added in the repository.
Confirm the precedence order across organization, course, and taxonomy levels before documenting it (existing internal docs disagree on the order).