Automate rollup configuration

[warm-coolguy]

https://github.com/Dataport/polar/pull/108#discussion_r1500270976

Rollup configuration files are currently hand-written, which is perfectly fine for the time being. To save us some time further down the line, we should try to automate their contents as described in this comment. The idea is to dynamically create configs at run-time from the package.json. This is also a deduplication effort.