* Make theme switcher accessible
* set an explicit `aria-label` to the switcher (as the `<span>` is not sufficient, as it can be display:none'd and then the button has no accName)
* make the theme buttons actual `aria-pressed` toggles
* Dynamically update aria-label for theme switcher
* Explicitly reset focus after activating theme
* Use innerText for the constructed dynamic aria-label
this way, if the text ever gets changed in the html, this will adapt appropriately
* Tweak accessible name for the dropdown
* Fixup
* Use `textContent` instead of `innerText`
