README: mention the CoC and who maintains this repo

Author: japaric

cortex-m-rt/README.md

@@ -5,6 +5,8 @@
 
 > Minimal runtime / startup for Cortex-M microcontrollers
 
+This project is developed and maintained by the [Cortex-M team][team].
+
 # [Documentation](https://docs.rs/cortex-m-rt)
 
 # License
@@ -23,3 +25,12 @@ at your option.
 Unless you explicitly state otherwise, any contribution intentionally submitted
 for inclusion in the work by you, as defined in the Apache-2.0 license, shall be
 dual licensed as above, without any additional terms or conditions.
+
+## Code of Conduct
+
+Contribution to this crate is organized under the terms of the [Rust Code of
+Conduct][CoC], the maintainer of this crate, the [Cortex-M team][team], promises
+to intervene to uphold that code of conduct.
+
+[CoC]: CODE_OF_CONDUCT.md
+[team]: https://github.com/rust-embedded/wg#the-cortex-m-team