Wrong typings for ESM module

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# Problem

TypeScript with ESM modules fails to compile a program importing this `@mapbox/mapbox-gl-language` package.

```typescript
import language from "@mapbox/mapbox-gl-language";

// This `default` property is `undefined`.
console.log(language.default);
// This `language` default export is the actual constructor. But this leads to a compile error.
const control = new language();
```

# References

- [A reproduction package](https://github.com/mapbox/raviqqe/tree/main/mapbox-gl-esm-typing)

Start with the linked reproduction package and its TypeScript ESM import of @mapbox/mapbox-gl-language. Compare the declared default export with the runtime value shown in the issue, then verify that the reproduction compiles while constructing the imported language control without accessing an undefined default property.

Written by the indexing model from the issue text.