Explore using vitejs or other bundlers for authui

When debugging https://github.com/authgear/authgear-server/issues/3796#issuecomment-1953401540, it's found that parceljs gets unexpected errors when we want to apply optimizations such as lazy loading.

A nice alternative is vitejs, which has built-in support for lazyloading and better suited for library mode since it's based on rollup.

Start by reading the debugging context in issue 3796 and reproducing the unexpected Parcel errors when applying lazy loading or other optimizations to authui. Compare Vite's lazy-loading support and library mode with the current setup; the issue does not name files, tests, or a specific acceptance criterion, so done is not defined.

Written by the indexing model from the issue text.