Add a "ci" feature to make clippy ignore docs warnings

plume-api/Cargo.toml

@@ -7,3 +7,6 @@ edition = "2018"
 [dependencies]
 serde = "1.0"
 serde_derive = "1.0"
+
+[features]
+ci = []

plume-api/src/lib.rs

@@ -1,4 +1,4 @@
-#![warn(missing_docs)]
+#![cfg_attr(not(feature = "ci"), warn(missing_docs))]
 
 #[macro_use]
 extern crate serde_derive;