Use the text theme toggle in the docs template

Andrew Dunnrequested to merge
chrome/toggle-markup-r2 into main

What does this MR do and why?

The docs template's header uses the text theme toggle the docs chrome now styles (!159 (merged)).

  • The sun and moon icons become the words light and dark.
  • The button's name is its visible text, and aria-pressed is true when the theme is dark.
  • Light is marked on in the markup for a page without script.

Test plan

  • just check adds no failure
  • Template builds with placeholders replaced

Merge request reports