chore: export composeCreateRsbuildConfig as utils (#367)

Author: nyqykk

packages/core/src/index.ts

@@ -1,6 +1,10 @@
 export { prepareCli } from './cli/prepare';
 export { runCli } from './cli/commands';
-export { defineConfig, loadConfig } from './config';
+export {
+  defineConfig,
+  loadConfig,
+  composeCreateRsbuildConfig as unstable_composeCreateRsbuildConfig,
+} from './config';
 export { build } from './build';
 export { logger } from './utils/logger';
 export type * from './types';