Add cargo metadata

Author: erickt

json/Cargo.toml

@@ -2,6 +2,12 @@
 name = "serde_json"
 version = "0.6.0"
 authors = ["Erick Tryzelaar <[email protected]>"]
+license = "MIT/Apache-2.0"
+description = "A JSON serialization file format"
+repository = "https://github.com/serde-rs/json"
+documentation = "https://serde-rs.github.io/json/serde_json/"
+readme = "../README.md"
+keywords = ["json", "serde", "serialization"]
 
 [dependencies]
 num = "*"