fix(multi-select): non-filterable MultiSelect should dispatch a blur event (#1080)

The non-filterable `MultiSelect` is missing a `blur` event.

Implementation-wise, we have to dispatch it and include the event as the `detail`. Otherwise, the filterable variant will dispatch "blur" twice because it has both a button and input.

The filterable `MultiSelect` continues to forward the blur event to the input.

tests/MultiSelect.test.svelte

@@ -17,6 +17,9 @@
     console.log(e.detail.selected);
     console.log(e.detail.unselected);
   }}"
+  on:blur="{(e) => {
+    e.detail; // number | FocusEvent
+  }}"
 />
 
 <MultiSelect