examples: add screenshot example (#1456)

docs/examples/screenshot/ScreenshotExample.vue

@@ -0,0 +1,17 @@
+<script lang="ts" setup>
+import sdk from '@stackblitz/sdk'
+
+const el = ref<HTMLDivElement>()
+
+onMounted(() => {
+  sdk.embedProjectId(el.value!, 'vitejs-vite-wnam9z', {
+    forceEmbedLayout: true,
+    openFile: 'src/App.vue',
+    height: 750,
+  })
+})
+</script>
+
+<template>
+  <div ref="el" class="outline-none"></div>
+</template>