Replace `tsc` with `rollup-plugin-dts` in build

[amannn]

Is your feature request related to a problem? Please describe.

We're currently using tsc to generate type definitions. This unfortunately drags in types from externals. We should investigate how we can switch to rollup-plugin-dts to correctly mark external types as such.

Describe the solution you'd like

Switch to rollup-plugin-dts or investigate if externals can be handled correctly with tsc.

Describe alternatives you've considered

I'm not aware of any externals config to be used with tsc.