feat: export EggModuleLoader in standalone (#146)

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##### Checklist
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- [ ] `npm test` passes
- [ ] tests and/or benchmarks are included
- [ ] documentation is changed or added
- [ ] commit message follows commit guidelines

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standalone/standalone/index.ts

@@ -1,3 +1,4 @@
+export * from './src/EggModuleLoader';
 export * from './src/Runner';
 export * from './src/main';
 export * from './src/StandaloneInnerObjectProto';