docs: fix v-model collapsed (#55)

Author: Akryum

docs/content/1.getting-started/2.usage.md

@@ -249,7 +249,7 @@ const collapsed = ref(false);
 </script>
 
 <template>
-  <SplitPanel v-model="collapsed">
+  <SplitPanel v-model:collapsed="collapsed">
     <!-- ... -->
   </SplitPanel>
 </template>
@@ -490,4 +490,4 @@ Uses the [Window Splitter WAI-ARIA pattern](https://www.w3.org/WAI/ARIA/apg/patt
 
 ::callout{icon="i-lucide-person-standing" color="warning"}
 The divider by default has no styling. Please add your own divider element to handle focus styles.
-::
+::