Offer alternative version of publish.js

[victorb]

Currently, publish.js is kind of big (3.6M on disk, 446KB gzipped) because we're not doing any minifying nor tree-shaking (which is hard when we want to evaluate arbitrary code). Biggest reason for not doing any minifying yet is because it'll make the errors a lot harder to understand when you're doing something wrong, so not sure if we can address that somehow.

But in the meantime, we could probably offer two versions of the publish.js. The first one being the existing one which is the full errors / non-minified one. And a second one which is minified/production/cryptic errors one, that people can use if they want to instead of the full-errors one.