change demo styling

demos/preview/Demo.vue

@@ -21,7 +21,7 @@
     </div>
     <div class="overflow-hidden rounded-b-xl">
       <div
-        class="border-2 border-black last:rounded-b-xl"
+        class="bg-white border-3 border-black last:rounded-b-xl"
         :class="[
           showTabs && firstTabSelected
             ? 'rounded-tr-xl'

demos/tailwind.config.js

@@ -8,6 +8,9 @@ module.exports = {
 
   theme: {
     extend: {
+      borderWidth: {
+        3: '3px',
+      },
       colors: {
         code: {
           attrName: '#faf594',