Standardize event names to be consistent with @headlessui-react

Was previously using Vue names since Vue was the primary reference while porting, but as the public API is closer to the React one it makes sense to use that.

Fixes #8

src/routes/listbox/_PeopleList.svelte

@@ -36,9 +36,9 @@
   <div class="space-y-1">
     <Listbox
       value={active}
-      on:updateValue={(event) => {
-        console.log("value:", event.detail.value);
-        active = event.detail.value;
+      on:change={(event) => {
+        console.log("value:", event.detail);
+        active = event.detail;
       }}
     >
       <ListboxLabel class="block text-sm font-medium leading-5 text-gray-700">