/**
Convert a camelized string into a lowercased one with a custom separator: `unicornRainbow` → `unicorn_rainbow`.

@param string - The camelcase string to decamelize.
@param separator - The separator to use to put in between the words from `string`. Default: `'_'`.

@example
```
import decamelize from 'decamelize';

decamelize('unicornRainbow');
//=> 'unicorn_rainbow'

decamelize('unicornRainbow', '-');
//=> 'unicorn-rainbow'
```
*/
export default function decamelize(string: string, separator?: string): string;