docs: updated nuxt bridge migration guide

docs/content/bridge/1.overview.md

@@ -149,6 +149,21 @@ Overwriting options such as `"compilerOptions.paths"` with your own configuratio
 In case you need to extend options provided by `./.nuxt/tsconfig.json` further, you can use the `alias` property withing your `nuxt.config`. `nuxi` will pick them up and extend `./.nuxt/tsconfig.json` accordingly.
 ::
 
+## Update Public Runtime Config References
+Nuxt 3 approaches runtime configs differently than Nuxt 2.  Now, all public runtime config properties are behind a property called `public`.  If you use public runtime configs, you'll need to update your code.
+
+```
+// nuxt.config.js
+publicRuntimeConfig: {
+  foo: 'bar'
+}
+```
+``` diff
+// MyWidget.vue
+- <div>Foo: {{ $config.foo }}</div>
++ <div>Foo: {{ $config.public.foo }}</div>
+```
+
 ## Migrate Composition API
 
 If you were using `@vue/composition-api` or `@nuxtjs/composition-api`, please read the [composition api migration guide](/bridge/bridge-composition-api).