Fix layout shift for scrollbars appearing/disapparing

Author: squidfunk

dist/assets/stylesheets/classic/main.2651815e.min.css

@@ -49,7 +49,7 @@
       {% if config.theme.variant == "modern" %}
         {% set href = 'assets/stylesheets/modern/main.eafc6f7f.min.css' | url %}
       {% else %}
-        {% set href = 'assets/stylesheets/classic/main.346a6e83.min.css' | url %}
+        {% set href = 'assets/stylesheets/classic/main.2651815e.min.css' | url %}
       {% endif %}
       <link rel="stylesheet" href="{{ href }}">
       {% if config.theme.palette %}

dist/assets/stylesheets/classic/main.346a6e83.min.css

@@ -36,6 +36,9 @@ html {
   // `font-size` of `12px` if the system language is set to Chinese. For this
   // reason we just double the `font-size` and set it to `20px`.
   font-size: 125%;
+  // Ensure that there's always enough space for scrollbars to avoid layout
+  // shifts without affecting operating systems that use overlay scrollbars
+  scrollbar-gutter: stable;
 
   // [screen medium +]: Set base `font-size` to `11px`
   @include break-from-device(screen medium) {