Let the docs table of contents scroll when it is taller than the viewport (#2994)

.changeset/fix-docs-toc-scroll.md

@@ -0,0 +1,5 @@
+---
+"@tabler/docs": patch
+---
+
+Fixed the docs "On this page" list running past the viewport; the sticky rail now scrolls on its own.

docs/scss/docs.scss

@@ -606,6 +606,10 @@ html {
 }
 
 // The table of contents sticks too, so it has to clear the header (#2421).
+// A long list must not run past the viewport either: the rail is capped at the
+// space below the header and scrolls on its own (#2965).
 .docs-toc-sticky {
   top: var(--docs-header-height);
+  max-height: calc(100vh - var(--docs-header-height));
+  overflow-y: auto;
 }