Improve tree-shaking

[dcastil]

Previously the entire tailwind-merge library was bundled into a single file. This has a few issues.

• It's harder to debug library as a library user during development as everything is in one huge file
• I rely on dead code elimination of the projects using the library to remove unused exports of tailwind-merge which should be fine for modern bundlers, but some bundlers don't do a good job with dead code elimination. It's better to rely on tree shaking with unused imports. A good example of this is Bundlephobia which reports that all exports of tailwind-merge use the entire bundle size which is not accurate.

Bundlephobias export analysis of tailwind-merge v1.0.0:

The solution: Preserve the transpiled files (at least for the ESM bundle) and don't bundle them into a single file.