Add Theseus OS to Operating Systems

README.md

@@ -278,6 +278,7 @@ See also [A comparison of operating systems written in Rust](https://github.com/
 * [nebulet/nebulet](https://github.com/nebulet/nebulet) — A microkernel that implements a WebAssembly "usermode" that runs in Ring 0.
 * [redox-os/redox](https://gitlab.redox-os.org/redox-os/redox) — [![build badge](https://api.travis-ci.org/redox-os/redox.svg?branch=master)](https://travis-ci.org/redox-os/redox)
 * [thepowersgang/rust_os](https://github.com/thepowersgang/rust_os) — [![build badge](https://api.travis-ci.org/thepowersgang/rust_os.svg?branch=master)](https://travis-ci.org/thepowersgang/rust_os)
+* [theseus-os/Theseus](https://github.com/theseus-os/Theseus) — A safe-language, single address space and single privilege level OS written from scratch in pure Rust - [![build badge](https://img.shields.io/github/workflow/status/theseus-os/Theseus/Documentation?label=docs%20build)](https://theseus-os.github.io/Theseus/book/index.html)
 * [tock/tock](https://github.com/tock/tock) — A secure embedded operating system for Cortex-M based microcontrollers
 
 ### Productivity