pipe "interesting" cargo.toml fields into the output manifest:

https://doc.rust-lang.org/cargo/reference/manifest.html#the-manifest-format

Currently with "1 binary = 1 release" this is a pretty straight-forward mapping. It will be more complicated when we support grouping things.

Start with the Cargo manifest format reference linked in the issue and trace how the current one-binary-to-one-release mapping produces the output manifest. Determine which Cargo.toml fields should be propagated and how that mapping should change when grouping is supported; done means the selected fields appear correctly without breaking grouped releases.

Written by the indexing model from the issue text.