feat(assets): new assets loading system (currently only for images)

app/pages/test.vue

@@ -0,0 +1,8 @@
+<script setup lang="ts">
+const { isReady } = useAssets();
+</script>
+
+<template>
+  <LoadingScreen v-if="!isReady" />
+  <p v-else>ok</p>
+</template>