Fixed V3.3.0 Common JS missing loadConfig and optimize exports

[nuintun]

esm

import { loadConfig, optimize } from 'svgo';

cjs

const { loadConfig, optimize } = require('svgo');

browser

import { optimize } from 'svgo/browser';

[SethFalco]

Thanks for investigating this as soon as you spotted the issue, and sorry for letting that through!

I'll be sure to check if there's any other public interfaces that we need to cover with tests too.

I've added a commit to your PR to at least add one test case, just to verify that loadConfig is defined. Once CI passes, happy to merge and I'll make a release. 👍🏽