update theme highlight

Author: carlagn

src/css/theming.css

@@ -8,6 +8,7 @@
   --code-with-result: var(--gray-800);
   --code-with-result-border: var(--code-with-result);
   --surface-brand-default: #16a394;
+  --docsearch-highlight-color: var(var(--surface-brand-default));
   --docsearch-searchbox-background: var(--ifm-color-secondary);
   --table-of-contents-link: rgb(113, 128, 150);
   --docsearch-modal-width: 1248px;