feat(AssetBrowserModal): set initial focus to SearchBox (#5945)

## Summary

Some quick design feedback.

## Changes

1. Fix the placeholder text so it's showing up correctly.
2. Make the SearchBox take initial focus when the modal is opened.

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-5945-feat-AssetBrowserModal-set-initial-focus-to-SearchBox-2846d73d365081bfb3e0cde78c827d5f)
by [Unito](https://www.unito.io)

src/platform/assets/components/AssetBrowserModal.vue

@@ -23,6 +23,7 @@
     <template #header>
       <SearchBox
         v-model="searchQuery"
+        :autofocus="true"
         size="lg"
         :placeholder="$t('assetBrowser.searchAssetsPlaceholder')"
         class="max-w-96"