Provided validation and helper slot for FwbSelect #242 (#254)

* feat(fwb-select): Add validation and helper slot

* docs(docs-select): Add validation and helper slot examples

docs/components/select/examples/FwbSelectExampleHelper.vue

@@ -0,0 +1,31 @@
+<template>
+  <div class="vp-raw">
+    <fwb-select
+      v-model="selected"
+      :options="countries"
+      label="Select a country"
+    >
+      <template #helper>
+        We'll never share your details. Read our
+        <fwb-a
+          href="#"
+          color="text-blue-600 dark:text-blue-500"
+        >
+          Privacy Policy
+        </fwb-a>.
+      </template>
+    </fwb-select>
+  </div>
+</template>
+
+<script lang="ts" setup>
+import { ref } from 'vue'
+import { FwbA, FwbSelect } from '../../../../src/index'
+
+const selected = ref('')
+const countries = [
+  { value: 'us', name: 'United States' },
+  { value: 'ca', name: 'Canada' },
+  { value: 'fr', name: 'France' },
+]
+</script>