docs(api): specify nuxt-error-boundary events and slots (#4159)

docs/content/3.api/2.components/5.nuxt-error-boundary.md

@@ -1,7 +1,33 @@
 # `<NuxtErrorBoundary>`
 
+Nuxt provides the `<NuxtErrorBoundary>` component to handle client-side errors happening in its default slot, using Vue's [`onErrorCaptured` hook.](https://vuejs.org/api/composition-api-lifecycle.html#onerrorcaptured)
+
+## Events
+
+- **@error**: Event emitted when the default slot of the component throws an error.
+
+  ```vue
+  <template>
+    <NuxtErrorBoundary @error="logSomeError">
+      <!-- ... -->
+    </NuxtErrorBoundary>
+  </template>
+  ```
+
+## Slots
+
+- **#error**: Specify a fallback content to display in case of error.
+
+  ```vue
+    <template>
+      <NuxtErrorBoundary>
+        <!-- ... -->
+        <template #error="{ error }">
+          <p>An error occured: {{ error }}</p>
+        </template>
+      </NuxtErrorBoundary>
+    </template>
+  ```
+
 ::ReadMore{link="/guide/features/error-handling"}
 ::
-
-::NeedContribution
-::