MAINTAINERS: add entry for the Rust num module

This new module provides numerical features useful for the kernel, such
as the `Integer` trait and the `Bounded` integer wrapper.

Signed-off-by: Alexandre Courbot <acourbot@nvidia.com>
Acked-by: Yury Norov (NVIDIA) <yury.norov@gmail.com>
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Link: https://patch.msgid.link/20251108-bounded_ints-v4-3-c9342ac7ebd1@nvidia.com
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>

Author: Gnurou

MAINTAINERS

@@ -22520,6 +22520,14 @@ T:	git https://github.com/Rust-for-Linux/linux.git alloc-next
 F:	rust/kernel/alloc.rs
 F:	rust/kernel/alloc/
 
+RUST [NUM]
+M:	Alexandre Courbot <acourbot@nvidia.com>
+R:	Yury Norov <yury.norov@gmail.com>
+L:	rust-for-linux@vger.kernel.org
+S:	Maintained
+F:	rust/kernel/num.rs
+F:	rust/kernel/num/
+
 RUST [PIN-INIT]
 M:	Benno Lossin <lossin@kernel.org>
 L:	rust-for-linux@vger.kernel.org