can't surpport Module Augmentation feature

[Module Augmentation](https://www.typescriptlang.org/docs/handbook/declaration-merging.html#module-augmentation)

for example
```
// ./typing.ts
declare module '~/lib/core' {
    interface Foo {
        foo(msg: string): void;
    }
}
// output
// ./dist/typing.d.ts
declare module '~/lib/core' {
    interface Foo {
        foo(msg: string): void;
    }
}
```