Add Customer nsSeparator To Typescript CustomTypeOptions

[vanenshi]

🚀 Feature Proposal

current typescript CustomTypeOptions provides a way to customize the keySeparator. but there is no options to change the nsSeparator.

Motivation

even though I have the ability to customize the nsSeparator in the i18n init function, I have no way to provide it to the CustomTypeOptions, hence it would be impossible to use nsSeparator without getting an error from typescript

Example

// i18n-resources.d.ts
import * as resources from './locales';

declare module 'react-i18next' {
  interface CustomTypeOptions {
    defaultNS: 'common';
    nsSeparator: '.';
    resources: typeof resources['en'];
  }
}

[adrai]

v11.15.7 should address this thanks to @pedrodurek