RDoc-3551 Fix color for hr

Author: mateuszbartosik

src/css/custom.css

@@ -408,4 +408,9 @@ code {
   @apply !border-0;
   border: 0 !important;
   box-shadow: none !important;
-}
+}
+
+/* Custom hr color */
+hr {
+  @apply !bg-black/10 dark:!bg-white/10;
+}