Bundle up the dist to avoid missing dependency issues

We've had some issues when trying to use `yarn link` where there were errors around multiple versions of React running and missing dependencies. After some investigation this appears to be related to the fact that this library doesn't bundle its dependencies like `classnames` and `nanoid` so they fail in projects that do not have those installed locally.

A fix, as discussed, was to bundle the project up with all dependencies and adding the current `peers` as `externals` so that they are not also bundled.

This was originally avoided because webpack didn't correctly tree-shake away exports that were not used. This appears to be resolved (although we should verify).