Template suggestion: derive

It would be nice to have a template for a crate + crate_derive combo, as a workspace.

e.g.

```
/
/src # root crate src
/crate_derive
/src # derive src
```

See https://github.com/bengreenier/enum_pipeline/

Review the repository's existing cargo-generate templates and compare them with the requested crate and crate_derive workspace structure. Use the referenced enum_pipeline project as an example, then verify that the new template generates a root crate with /src and a crate_derive crate with its own /src.

Written by the indexing model from the issue text.