fix dark mode settings

Signed-off-by: Prajwol Amatya <prajwolamatya11@gmail.com>

Author: PrajwolAmatya

src/App.vue

@@ -411,15 +411,15 @@ function applyTemplateIfNeeded() {
 <style lang="scss">
 .dark-mode {
   .reveal {
-    color: var(--oc-color-text-default) !important;
+    color: var(--oc-color-text-default, var(--color-role-on-surface)) !important;
 
     h1,
     h2,
     h3,
     h4,
     h5,
     h6 {
-      color: var(--oc-color-text-default) !important;
+      color: var(--oc-color-text-default, var(--color-role-on-surface));
     }
 
     code {