{{- /* Light/dark switch, sitting at the end of the masthead. The button holds no state of its own. Which face the icon wears, and which of the two labels is its accessible name, both follow the `data-theme` attribute on through CSS alone - see the `dark` mixin in style.scss. That is not neatness for its own sake: hx-boost morphs a freshly rendered copy of this markup in on every navigation, so anything a script had written onto the element would be quietly reverted, while is never swapped and carries the choice across the whole visit untouched. Two labels rather than one, with CSS showing exactly one at a time, so the button announces the action it performs ("switch to dark theme") instead of a state the reader then has to interpret. display:none is what keeps the other out of the accessible name. */ -}}