feat: Add clippy lint for mut calls in a debug_assert (#488)

https://rust-lang.github.io/rust-clippy/master/index.html#/debug_assert_with_mut_call

src/lib.rs

@@ -1,5 +1,3 @@
-#![warn(missing_docs)]
-
 //! `hugr` is the Hierarchical Unified Graph Representation of quantum circuits
 //! and operations in the Quantinuum ecosystem.
 //!
@@ -9,6 +7,11 @@
 //!   structures.
 //!
 
+#![warn(missing_docs)]
+// Unstable check, may cause false positives.
+// https://github.com/rust-lang/rust-clippy/issues/5112
+#![warn(clippy::debug_assert_with_mut_call)]
+
 pub mod algorithm;
 pub mod builder;
 pub mod extension;