GitHub: add Zulip to the README

Signed-off-by: Miguel Ojeda <ojeda@kernel.org>

Author: ojeda

README.md

@@ -4,7 +4,7 @@ The goal of this project is to add support for the Rust language to the Linux ke
 
 Feel free to [contribute](https://github.com/Rust-for-Linux/linux/contribute)! To start, take a look at [`Documentation/rust`](https://github.com/Rust-for-Linux/linux/tree/rust/Documentation/rust).
 
-General discussions, announcements, questions, etc. take place on the mailing list at rust-for-linux@vger.kernel.org ([subscribe](mailto:majordomo@vger.kernel.org?body=subscribe%20rust-for-linux), [instructions](http://vger.kernel.org/majordomo-info.html), [archive](https://lore.kernel.org/rust-for-linux/)).
+General discussions, announcements, questions, etc. take place on the mailing list at rust-for-linux@vger.kernel.org ([subscribe](mailto:majordomo@vger.kernel.org?body=subscribe%20rust-for-linux), [instructions](http://vger.kernel.org/majordomo-info.html), [archive](https://lore.kernel.org/rust-for-linux/)). For chat, help, quick questions, informal discussion, etc. you may want to join our Zulip at https://rust-for-linux.zulipchat.com ([request an invitation](https://lore.kernel.org/rust-for-linux/CANiq72kW07hWjuc+dyvYH9NxyXoHsQLCtgvtR+8LT-VaoN1J_w@mail.gmail.com/T/)).
 
 All contributors to this effort are understood to have agreed to the Linux kernel development process as explained in the different files under [`Documentation/process`](https://www.kernel.org/doc/html/latest/process/index.html).