style: Use deeper indentation for wide display

Author: toshimaru

src/_sass/railsdoc.scss

@@ -180,6 +180,10 @@ code {
     .method__aka,
     .method__source {
         margin-left: 1em;
+
+        @media (min-width: 768px) {
+            margin-left: 2em;
+        }
     }
 }