Awesome work on unpkg! We're using it a lot for the A-Frame ecosystem.

Currently for unpkg, we can specify main or browser fields such that a unpkg.com/my-package/ will resolve to a file we specify. But this overloads main and browser:

• Some authors would like to keep main pointing to their pre-built entry point (e.g., index.js), maybe to npm link or to differentiate browser builds from npm builds.
• Some authors would like to not like to specify browser because that is used by Browserify, and specifying it can mess up build steps.

Perhaps an unpkg specific one? {"cdn": "dist/mybuild.min.js"}