fes.js/packages/fes-plugin-locale/types.d.ts

import '@fesjs/fes';

declare module '@fesjs/fes' {
    interface PluginBuildConfig {
        locale?:
            | {
                  locale: string;
                  fallbackLocale: string;
                  baseNavigator: boolean;
                  legacy: boolean;
              }
            | false;
    }

    // export * from 'vue-i18n';

    export const locale: {
        setLocale({ locale }: { locale: string }): void;
        addLocale({ locale, messages }: { locale: string; messages: object }): void;
        getAllLocales(): string[];
        messages: Record<string, object>;
    };
}