[Release Docs] Add documentation and release notes for separate Competency Management and Taxonomy Editing screens

[mgwozdz-unicon]

This issue adds documentation and release notes for the new workflow that separates the Competency Criteria screen from the Taxonomy Editing screen. The documentation should explain how to access each screen from the vertical ellipses menu, when to select “Apply Competencies,” and when to select “Edit Taxonomy.”

Outstanding/Needs Confirmation:

• Last time docs were put here: https://github.com/openedx/docs.openedx.org
• Where/how should release notes be written?
• Anything else we should be aware of?