fix: allow internal_features when opting in via unstable feature

Signed-off-by: Martin Kröning <[email protected]>

Author: mkroening

src/lib.rs

@@ -40,6 +40,7 @@
 #![cfg_attr(feature = "very_unstable", feature(fn_traits))]
 #![cfg_attr(feature = "very_unstable", feature(effects))]
 #![cfg_attr(docsrs, feature(doc_auto_cfg))]
+#![cfg_attr(feature = "unstable", allow(internal_features))]
 #![warn(missing_docs)]
 #![deny(unsafe_op_in_unsafe_fn)]
 #![doc(test(attr(deny(warnings))))]