feat: add Tailwind CSS via its own CLI

tailwind/_utilities.css

@@ -0,0 +1,7 @@
+@layer utilities {
+    /* Reserve the scrollbar gutter so content does not shift width when a
+       scrollbar appears (e.g. when a collapsible section is opened). */
+    .scroll-stable {
+        scrollbar-gutter: stable;
+    }
+}