Minor readme tweaks [skip ci]

Author: Shatur

README.md

@@ -20,7 +20,8 @@ If you are new to networking, see [glossary](https://gist.github.com/maniwani/f9
 - Abstracts game logic to support singleplayer, client, dedicated server, and listen server configurations simultaneously.
 - No builtin I/O, can be used with any messaging library. See [messaging backends](#messaging-backends) for already available integrations.
 - Heavily optimized.
-- Works with `no_std`.
+- Robust, with high test coverage.
+- Supports `no_std` and environments without atomic CAS, such as thumbv6m.
 - Hackable. See [ecosystem](#ecosystem).
 
 ## Getting Started