enable hljs

src/client/styles/scss/_override-bootstrap-variables.scss

@@ -82,6 +82,9 @@ $progress-border-radius: 0;
 $progress-bg: #f0f0f0;
 $progress-box-shadow: none;
 
+//== Code
+$pre-color: dummyinvalildcolor; // disable pre color specification with invalid value
+
 //== Custom Checkbox
 $custom-checkbox-indicator-border-radius: 0px;
 $custom-control-indicator-focus-box-shadow: none;

src/client/styles/scss/theme/_apply-colors.scss

@@ -42,7 +42,7 @@ $input-focus-color: $color-global;
   }
 }
 
-pre {
+pre:not(.hljs) {
   background-color: $bgcolor-inline-code;
   border-color: $bordercolor-inline-code;
 }