Improve package build

[avsetsin]

The current build consumes a lot of memory. I guess the hardest part is generating typescript declarations. We can try to put it in a separate step. Also, we can only generate declarations for the esm version because package.json refers only to them. I guess that might help a little bit.

Or we could try a completely different approach. For example esbuild. This is a super fast and it shouldn't consume so many resources