devDependencies are bundled even if they are in peerDependencies as well

According to the readme:

> By default tsup bundles all import-ed modules but `dependencies` and `peerDependencies` in your package.json are always excluded.

So, I would think that if peerDependencies are always excluded, then if I specify a dependency in both `devDependencies` _and_ `peerDependencies` (meaning, it's a peer dependency, but when I'm working on developing the package, I also want it to be installed), then it should not be bundled.

But, this is not the behavior I am seeing. Instead, the dependency is bundled into the build, unless I explicitly add it to `externals`. Is this intentional, or a bug? If it's intentional, maybe the README can be clarified to avoid such confusion?

Start by reproducing the case with a package.json that lists the same dependency in both devDependencies and peerDependencies, then compare the result with the README statement that peerDependencies are excluded. Check how tsup determines which imports to bundle and whether the behavior or documentation matches the stated expectation.

Written by the indexing model from the issue text.