fix: make it work when paired with @vue3 + @vue/compat

TL;DR - default vue-compat mode is `2` which makes slots behave like vue 2 (not functions) but our isVue3 still evals to true, forwarding access to the correct property but that is not a function because of compat mode.

This config overrides it.

Author: renatodeleao

src/A11yDialog.vue

@@ -27,6 +27,9 @@ const getInitialState = () => ({
 export const VALID_ROLES = ["dialog", "alertdialog"];
 
 export default {
+  compatConfig: {
+    MODE: 3 // opt-in to Vue 3 if loaded in compat mode
+  },
   name: "a11y-dialog",
   emits: ['show', 'hide', 'close'],
   props: {