Add "commont metadata" to Cargo.toml

Author: qryxip

Cargo.toml

@@ -3,6 +3,11 @@ name = "ac-library-rs"
 version = "0.1.0"
 authors = ["matsu7874 <[email protected]>"]
 edition = "2018"
+description = "A Rust port of AtCoder Library (ACL)."
+license = "CC0-1.0"
+repository = "https://github.com/rust-lang-ja/ac-library-rs"
+keywords = ["competitive"]
+categories = ["algorithms", "data-structures"]
 publish = false
 
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html