Project: webpack
Task (challenging): I want to implement the following functionality with bundler.

For example:
```js
import md from './hello.md'
```
If langauge is 'en', `./hello.md` will resolved to `./hello.en.md` if it exists.
If langauge is 'zh', `./hello.md` will resolved to `./hello.zh.md` if it exists.
If both `./hello.en.md` and `./hello.zh.md` are not found, fallback to its original path `./hello.md`

Besides this, use language="zh" as default value when resolving file.