Esbuild Escape Hatch

It would be very useful to have direct access to the esbuild launch args. Similar to esbuildPlugins, a "esbuildParams" would be useful in one off situations where the tsup API does not provide functionality.

As an example, it would be great if we could provide an output file name and not just an outDir. The work around I've come up with for now is to write a custom plugin to rename the assets at the end.

I can absolutely appreciate the philosophy of "this is a wrapper" and for advanced cases use esbuild directly. However, I am trying to standardize our tooling and having direct access would allow us to standardize on tsup.

Start by tracing where tsup invokes esbuild and how the existing esbuildPlugins option is exposed. Compare the requested direct launch-argument access with the current outDir behavior; done means callers can pass supported esbuild parameters, including an output file name, without a custom renaming plugin.

Written by the indexing model from the issue text.