Add Unity Social SDK sample (#7827)

Author: anthonydiscord

docs/discord-social-sdk/getting-started/using-unity.mdx

@@ -881,7 +881,15 @@ Congratulations! You've successfully integrated the Discord Social SDK into Unit
 
 ## Next Steps
 
-You have successfully set up the Discord Social SDK with Unity and authenticated with Discord!You can now use the SDK to add more social features in your project.
+### Social SDK Unity sample
+
+Check out our [in depth sample for using the Social SDK in Unity](https://github.com/discord/social-sdk-unity-sample) following the best practices laid out in these guides. It contains easy to drop in prefabs with both code and UI to quickly integrate Discord's social features into your game.
+
+![Video showing off the Unity sample with the Discord Social SDK](images/social-sdk/getting-started/unity-sample-preview.webp)
+
+### Continuing On
+
+Follow these guides to dive deeper into the features of the Discord Social SDK.
 
 <Container>
   <Card title="Creating a Unified Friends List" link="/docs/discord-social-sdk/development-guides/creating-a-unified-friends-list" icon="ListViewIcon">