Add badges to Cargo.toml

Author: kpp

Cargo.toml

@@ -10,6 +10,13 @@ repository = "https://github.com/kpp/futures-async-combinators"
 keywords = ["async", "await", "futures"]
 edition = "2018"
 
+[badges]
+travis-ci = { repository = "kpp/futures-async-combinators" }
+coveralls = { repository = "kpp/futures-async-combinators" }
+# Available options are `actively-developed`, `passively-maintained`,
+# `as-is`, `none`, `experimental`, `looking-for-maintainer`, `deprecated`.
+maintenance = { status = "experimental" }
+
 [dependencies]
 pin-utils = "=0.1.0-alpha.4"