Module/nomodule output

[developit]

It is now possible to use multiple outputs (but the same rollup compilation) to generate bundles with different manualChunks option.

Also enabled for multi-output in rollup/rollup#3645, the inlineDynamicImports option might make it easy for us to generate an ssr-bundle.js quickly without adding much overhead to prod builds.

[developit]

I implemented this in one of the test fixtures. We can extract it to packages/ and publish:
https://github.com/developit/wmr/blob/1b008a9916c6cee21169946fdc0b5628f294099e/test/fixtures/config/wmr.config.js#L9

[developit]

An initial implementation has been published as a plugin in #196:

// npm install @wmr-plugins/nomodule

import nomodule from '@wmr-plugins/nomodule';
export function build(config) {
  nomodule(config);
}