docs(ffi): add unstable feature flag to module in docsrs

Author: seanmonstar

src/ffi/mod.rs

@@ -25,7 +25,7 @@
 //! `cargo`, staring with `1.64.0`, it can be compiled with the following command:
 //!
 //! ```notrust
-//! RUSTFLAGS="--cfg hyper_unstable_ffi" cargo rustc --features client,http1,http2,ffi --crate-type cdylib
+//! RUSTFLAGS="--cfg hyper_unstable_ffi" cargo rustc --crate-type cdylib --features client,http1,http2,ffi
 //! ```
 
 // We may eventually allow the FFI to be enabled without `client` or `http1`,

src/lib.rs

@@ -79,6 +79,7 @@ pub mod service;
 pub mod upgrade;
 
 #[cfg(feature = "ffi")]
+#[cfg_attr(docsrs, doc(cfg(all(feature = "ffi", hyper_unstable_ffi))))]
 pub mod ffi;
 
 cfg_proto! {