Move to tsup.

[hitesh-32f]

We accidentally started this project using tsdx . tsdx is abandoned by its author. There's a fork of it: dts-cli. We are using it for time being. We should move away form it and use tsup.. tsdx is on older version of typescript and has cause many issues with build and linting. We have done custom setup for almost everything. Things are not in good shape because of this. We should move away asap.

cc: @sarat1669