fix(docs): prevent scrollbar layout shift on icons page (#4500)

Adds scrollbar-gutter: stable to html to reserve space for the scrollbar,
preventing layout shift when navigating to/from the icons route.

docs/.vitepress/theme/style.css

@@ -67,6 +67,10 @@
   animation: .3s transition 0s ease;
 } */
 
+html {
+  scrollbar-gutter: stable;
+}
+
 .VPHome {
   overflow-x: hidden;
 }