feat(module): implement --ui-radius CSS variable (#2341)

Co-authored-by: Benjamin Canac <canacb1@gmail.com>

docs/app/app.vue

@@ -52,6 +52,7 @@ const links = computed(() => {
 })
 
 const color = computed(() => colorMode.value === 'dark' ? (colors as any)[appConfig.ui.colors.neutral][900] : 'white')
+const radius = computed(() => `:root { --ui-radius: ${appConfig.theme.radius}rem; }`)
 
 useHead({
   meta: [
@@ -62,6 +63,9 @@ useHead({
     { rel: 'icon', type: 'image/svg+xml', href: '/icon.svg' },
     { rel: 'canonical', href: `https://ui.nuxt.com${withoutTrailingSlash(route.path)}` }
   ],
+  style: [
+    { innerHTML: radius, id: 'nuxt-ui-radius', tagPriority: -2 }
+  ],
   htmlAttrs: {
     lang: 'en'
   }