docs: improve forms usage with examples

docs/content/3.forms/6.radio.md

@@ -5,11 +5,36 @@ description: Display a radio field.
 
 ## Usage
 
-::component-card
----
-baseProps:
-  name: 'radio'
----
+Use a `v-model` to make the Radio reactive.
+
+::component-example
+#default
+:radio-example
+
+#code
+```vue
+<script setup>
+const methods = [{
+  name: 'email',
+  value: 'email',
+  label: 'Email'
+}, {
+  name: 'sms',
+  value: 'sms',
+  label: 'Phone (SMS)'
+}, {
+  name: 'push',
+  value: 'push',
+  label: 'Push notification'
+}]
+
+const selected = ref('sms')
+</script>
+
+<template>
+  <URadio v-for="method of methods" :key="method.name" v-model="selected" v-bind="method" />
+</template>
+```
 ::
 
 ### Label