It would be useful for Crates.io API to surface is_proc_macro

[dzbarsky]

Current Behavior

It doesn't look possible to tell from the API whether a crate's lib is a proc macro. Tools using the API are unable to tell if a crate is a proc macro without downloading it and examining the Cargo.toml.

Expected Behavior

The API already surfaces some fields describing what's in the crate, such as bin_names and has_lib. It would be useful to also surface is_proc_macro: [true/false] depending on whether "proc-macro = true" is set in the Cargo.toml.

Steps To Reproduce

1. Go to https://crates.io/api/v1/crates/serde_derive/1.0.204
2. No indication that this is a proc macro

Environment

• Browser:
• OS:

Anything else?

No response