[BUG] Many duplicated type files

[veksa]

Before you begin...

• I have searched the existing issues
• I am not using version 13.x of node (if so, please upgrade)

Description of the problem

After switching to building with tsc (#763), the resulting bundles contain many duplicate type files for each bundle type (CJS, ESM, etc.).

This can be resolved by generating types only once, instead of doing it for each bundle separately.

This can be achieved by building with tsup (https://github.com/egoist/tsup).

Recipe for reproducing

No response

Additional information

No response

Environment

No response

[broofa]

Other than increasing the package size (by ~400K), can you elaborate on what adverse impacts this has?

I'm open to ways to dedupe the type files but the current setup is simple and obvious, which tends to pay dividends when it comes to maintainability.

Regarding tsup, not having used it before it's not clear to me how it helps. For example, tsup src --format cjs,esm --dts --clean --sourcemap results in a dist directory that's 30% larger than what we have currently (1.9M vs 1.4M) ... and that doesn't include browser-specific builds.

If you'd like to put up a PR that shows how you'd solve this issue, I'd be curious to see what you have in mind.