Feature: provide Options Type as export to webpack plugin

[ntucker]

Describe the enhancement

Easy way to know and use the type of the webpack plugin.

Motivation

used to be able to do
import { PluginOptions } from '@wyw-in-js/babel-preset'; to get the webpack options, but now that's not even possible.

mini-css-extract-plugin does the following

import { PluginOptions } from 'mini-css-extract-plugin';

sass-loader does

import type { Options } from 'sass-loader';

I use these to construct options for my webpack config that pre-includes the best plugins in the ecosystem (including linaria/www-in-js) (see https://github.com/ntucker/anansi/blob/master/packages/webpack-config-anansi/index.d.ts)

Possible implementations

import { PluginOptions } from '@wyw-in-js/webpack';