add workflow badge

readme.md

@@ -1,6 +1,7 @@
 # Vers - Very Efficient Rank and Select
 
 [![crates.io](https://img.shields.io/crates/v/vers-vecs.svg)](https://crates.io/crates/vers-vecs)
+![rust](https://github.com/cydhra/vers/actions/workflows/rust.yml/badge.svg)
 [![docs](https://docs.rs/vers-vecs/badge.svg)](https://docs.rs/vers-vecs)
 
 Vers (vers-vecs on crates.io)
@@ -160,4 +161,4 @@ It is redistributed under the above dual license.
 ## Contribution
 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.
+dual licensed as above, without any additional terms or conditions.