Load plugins in browser environment

Describe the bug

Currently plugins don't work in browser env.

To Reproduce
Steps to reproduce the behavior:

import { createConfig, makeDocumentFromString } from '@redocly/openapi-core';

const openapi = `
  openapi: "3.0.0"
  info:
    version: 1.0.0
    title: Swagger Petstore
`;

const document = makeDocumentFromString(openapi, '/some-path');

const config = await createConfig(`
  lint:
    plugins:
      - './local-plugin.js'
  extends:
    - recommended
`);

const problems = await lintDocument({
  document,
  config: config.styleguide,
});

5. See error
   Cannot load ./local-plugin.js. Plugins aren't supported in browser yet.

Expected behavior

Plugin should be loaded and ran

Redocly Version(s)

v1.0.0-beta.108

Additional context

Browser

Start with the browser reproduction using createConfig, makeDocumentFromString, and lintDocument from @redocly/openapi-core, then trace the source of the "Plugins aren't supported in browser yet" error. Done means the shown local plugin configuration loads and runs in a browser environment without that error.