feat(root): use tsdown instead of tsup#1

cubic-dev-local[bot] wants to merge 5 commits intoeval-pr-2453-target-1758205412797mrge-io/eval-react-email:eval-pr-2453-target-1758205412797from

eval-pr-2453-violation-1758205412797mrge-io/eval-react-email:eval-pr-2453-violation-1758205412797Copy head branch name to clipboard