Add description field to userfaultfd-sys package.

Author: tyler

userfaultfd-sys/Cargo.toml

@@ -4,6 +4,7 @@ version = "0.1.0"
 authors = ["Adam C. Foltzer <[email protected]>"]
 edition = "2018"
 license = "MIT OR Apache-2.0"
+description = "Low-level bindings for userfaultfd functionality on Linux."
 
 build = "build.rs"