docs: perf dark (#5440)

Co-authored-by: caijun <caijun@gumingnc.com>

components/grid/demo/playfround.vue

@@ -70,6 +70,7 @@ A simple playground for column count and gutter.
     <pre
       >{{ rowColHtml }}
     </pre>
+    <br />
     <pre
       >{{ rowColHtml }}
     </pre>
@@ -138,4 +139,7 @@ export default defineComponent({
   font-size: 13px;
   padding: 8px 16px;
 }
+[data-theme='dark'] #components-grid-demo-playground pre {
+  background: #2f2f2f;
+}
 </style>

components/steps/demo/step-next.vue

@@ -85,4 +85,9 @@ export default defineComponent({
 .steps-action {
   margin-top: 24px;
 }
+
+[data-theme='dark'] .steps-content {
+  background-color: #2f2f2f;
+  border: 1px dashed #404040;
+}
 </style>