small refactorings and cleanups, improved bun/node adapter, updated docs

docs/integration/bun.mdx

@@ -16,7 +16,8 @@ the admin panel.
 // index.ts
 import { serve } from "bknd/adapter/bun";
 
-const handler = serve({
+// if the configuration is omitted, it uses an in-memory database
+serve({
    connection: {
       type: "libsql",
       config: {
@@ -25,13 +26,6 @@ const handler = serve({
       }
    }
 });
-
-Bun.serve({
-   port: 1337,
-   fetch: handler
-});
-
-console.log("Server running at http://localhost:1337");
 ```
 For more information about the connection object, refer to the [Setup](/setup) guide.