update(examples): Add validation and zoom pan helper example

examples/Validation/CustomInput.vue

@@ -0,0 +1,9 @@
+<script lang="ts" setup>
+import { Position, Handle, Connection } from '~/index'
+
+const isValidConnection = (connection: Connection) => connection.target === 'B'
+</script>
+<template>
+  <div>Only connectable with B</div>
+  <Handle type="source" :position="Position.Right" :is-valid-connection="isValidConnection" />
+</template>