Option `include` with same named locale files should be merged

eg.

My Config
```js
vueI18n({
include: ['./myProject/submodule/locales/**', './myProject/locales/**']
})
```

And my locale files could be places here:
```sh
├── ./myProject/
│ ├── ./submodule/locales/en.yaml
│ ├── ./locales/en.yaml
```

Only `'./myProject/submodule/locales/**'` works right now.