feat: add SvelteKit adapter

Add framework adapter for SvelteKit with:
- `getApp()` - get bknd app instance
- `serve()` - request handler for hooks.server.ts

Usage in hooks.server.ts:
```typescript
import { serve } from "bknd/adapter/sveltekit";
import config from "../bknd.config";

const bkndHandler = serve(config);

export const handle = async ({ event, resolve }) => {
  if (event.url.pathname.startsWith("/api/")) {
    return bkndHandler(event);
  }
  return resolve(event);
};
```

Includes:
- Adapter implementation (app/src/adapter/sveltekit/)
- Test suite
- Working example (examples/sveltekit/)
- Package exports and types

examples/sveltekit/package.json

@@ -0,0 +1,23 @@
+{
+  "name": "bknd-sveltekit-example",
+  "version": "0.0.1",
+  "private": true,
+  "scripts": {
+    "dev": "vite dev",
+    "build": "vite build",
+    "preview": "vite preview"
+  },
+  "devDependencies": {
+    "@sveltejs/adapter-auto": "^7.0.0",
+    "@sveltejs/kit": "^2.0.0",
+    "@sveltejs/vite-plugin-svelte": "^6.0.0",
+    "svelte": "^5.0.0",
+    "typescript": "^5.0.0",
+    "vite": "^7.0.0"
+  },
+  "dependencies": {
+    "bknd": "file:../../app",
+    "@libsql/client": "^0.15.0"
+  },
+  "type": "module"
+}