Fix Tsup setup to fuel docs with twenty-ui components

[charlesBochet]

Context

We are using tsup to extract a subset of components from ./packages/twenty-front (especially UI components), build and make them available in ./packages/twenty-docs
Recently the tsup command was broken due to monorepo migration

What

This PR is fixing the setup. From now, to run it:
yarn nx tsup twenty-front

then:
yarn nx start twenty-docs