Using Rollup with shared helpers always includes transitionManager

[Conduitry]

This is probably technically in Rollup's court, but if there's anything we can do here to make the bundler behave better, that would be nice to do.

If you import any of the helpers in shared.js and bundle with Rollup with default settings, the transitionManager comes along too. I assume this has to do with it being an object instead of a function, and Rollup can't tell that it has no side effects.

FWIW, UglifyJS is able to discern that this is unneeded code and remove it, but Butternut is not. So maybe this is even in Butternut's court.

[Rich-Harris]

Ah, curses. Rollup should be detecting and removing that. It might need to be written in a slightly different way.

Ideally Butternut would also detect and remove it, but the earlier it happens in the process the better.