As a user, I want to be able to turn Dark Mode on/off with a simple toggle.
Based on the outcome of T221809: Design UI for turning dark mode on and off , build a feature to allows users to one-click toggle Dark Mode. This link should be available to users that are logged in or are not logged in. The current state of the toggle should be maintained in localStorage for the user's client.
User interface changes
Does this need QA?