Consider Replacing `rollup-plugin-dts` with another option

[While using TSUp for TanStack Form](https://github.com/TanStack/form/pull/462), I ran into an issue where `this` in a class context was being replaced with `this$1` incorrectly.

As it turns out, this is a bug in `rollup-plugin-dts`: https://github.com/Swatinem/rollup-plugin-dts/issues/279

This in itself isn't a good reason to replace the package, however it seems that while I was investigating I saw that the package is in maintainance mode: https://github.com/Swatinem/rollup-plugin-dts/issues/277

Which might be a good enough reason to migrate off of the tool.

Start by reviewing TSUp's current integration with rollup-plugin-dts and reproduce the reported class-context issue from the linked TanStack Form work. Compare viable alternatives, then verify that the selected migration avoids the reported bug and preserves TypeScript declaration bundling.

Written by the indexing model from the issue text.