Language support is not working

I use version 2.0.1, and I found out that 'language' is not allowed.

Is there any plan to allow all languages to be used? If not, it would be nice to modify the README. The README said all languages are allowed.

```
[
require.resolve('docusaurus-plugin-search-local'),
{
hashed: true,
language: "ko"
}
],
```