What problem does this feature solve?

Can the copy plugin handle and preserve whatever permissions the underlying OS/filesystem the source files had?

This will eliminate the need to create a separate pre-packaging step just to fixup permission which may be error prone where config gets out of sync with artifacts

What does the proposed API of configuration look like?

{
  output: {
    copy: [
      { from: "./my-file.sh", copyPermissions?: true },
    ]
  }
}