docs: add README (#4)

Author: Taure

README.md

@@ -0,0 +1,79 @@
+# asobi-unity
+
+Unity client SDK for the [Asobi](https://asobi.dev) game backend. Unity 2021.3+, pure C#.
+
+## Installation
+
+Add via Unity Package Manager using the git URL:
+
+```
+https://github.com/widgrensit/asobi-unity.git
+```
+
+Window > Package Manager > + > Add package from git URL...
+
+## Quick Start
+
+```csharp
+using Asobi;
+
+var client = new AsobiClient("localhost", port: 8080);
+
+// Auth
+await client.Auth.Register("player1", "secret123");
+await client.Auth.Login("player1", "secret123");
+
+// REST APIs
+var player = await client.Players.GetSelf();
+var top = await client.Leaderboards.GetTop("weekly");
+var wallets = await client.Economy.GetWallets();
+
+// Real-time
+client.Realtime.OnMatchState += (state) => Debug.Log($"Tick: {state["tick"]}");
+await client.Realtime.ConnectAsync();
+await client.Realtime.AddToMatchmaker("arena");
+```
+
+## Features
+
+- **Auth** - Register, login, token refresh
+- **Players** - Profiles, updates
+- **Matchmaker** - Queue, status, cancel
+- **Matches** - List, details
+- **Leaderboards** - Top scores, around player, submit
+- **Economy** - Wallets, store, purchases
+- **Inventory** - Items, consume
+- **Social** - Friends, groups, chat history
+- **Tournaments** - List, join
+- **Notifications** - List, read, delete
+- **Storage** - Cloud saves, key-value
+- **IAP** - In-app purchase receipt validation
+- **Realtime** - WebSocket for matches, chat, presence, matchmaking
+
+## API Reference
+
+All API modules are accessible from `AsobiClient`:
+
+| Property | Class |
+|----------|-------|
+| `Auth` | `AsobiAuth` |
+| `Players` | `AsobiPlayers` |
+| `Matchmaker` | `AsobiMatchmaker` |
+| `Matches` | `AsobiMatches` |
+| `Leaderboards` | `AsobiLeaderboards` |
+| `Economy` | `AsobiEconomy` |
+| `Inventory` | `AsobiInventory` |
+| `Social` | `AsobiSocial` |
+| `Tournaments` | `AsobiTournaments` |
+| `Notifications` | `AsobiNotifications` |
+| `Storage` | `AsobiStorage` |
+| `IAP` | `AsobiIAP` |
+| `Realtime` | `AsobiRealtime` |
+
+## Demo
+
+See [asobi-unity-demo](https://github.com/widgrensit/asobi-unity-demo) for a complete example project.
+
+## License
+
+Apache-2.0