fix(types): export Config type from package

[aloisklink]

Summary

This PR exports the Config type from DOMPurify, so that people can do:

import type {Config} from 'dompurify';

// or
type Config = import('dompurify').Config;

Background & Context

This is to more closely match @types/dompurify, which allows it, to make migration easier for any TypeScript users that currently use @types/dompurify.

Tasks

N/A

Dependencies

N/A

[cure53]

This looks great, thank you :)