a11y(darkmode): use a button for the theme toggle (#1335)

Andrew

2024-08-24 4c9e8601504f76dcc3c273ea8ad1862df432b7b4

 quartz/styles/variables.scss

@@ -4,3 +4,6 @@
$sidePanelWidth: 380px;
$topSpacing: 6rem;
$fullPageWidth: $pageWidth + 2 * $sidePanelWidth;
$boldWeight: 700;
$semiBoldWeight: 600;
$normalWeight: 400;