Fixed tsup configuration

Fixed tsup build error. It was caused by the recent switch to typescript project references. I set the tsup config file to use tsconfig.src.json and commented out composite: true in the tsconfig. Technically, it should be set to true for projects using project references but everything seems to be working normally without it.

I also added a tsup CI build job to find tsup errors earlier and prevent merging to main with a failing build.

Closes #46 (closed)