feat: add integration of serde_json

Author: chirino

README.md

@@ -74,6 +74,7 @@ your Schemas automatically.
 - [chrono][chrono]
 - [chrono-tz][chrono-tz]
 - [bson][bson]
+- [serde_json][serde_json]
 
 ### Web Frameworks
 
@@ -120,3 +121,4 @@ Juniper has not reached 1.0 yet, thus some API instability should be expected.
 [chrono-tz]: https://crates.io/crates/chrono-tz
 [bson]: https://crates.io/crates/bson
 [juniper-from-schema]: https://github.com/davidpdrsn/juniper-from-schema
+[serde_json]: https://crates.io/crates/serde_json

juniper/Cargo.toml

@@ -25,11 +25,13 @@ default = [
     "schema-language",
     "url",
     "uuid",
+    "json",
 ]
 expose-test-schema = ["anyhow", "serde_json"]
 graphql-parser-integration = ["graphql-parser"]
 scalar-naivetime = []
 schema-language = ["graphql-parser-integration"]
+json = ["serde_json"]
 
 [dependencies]
 juniper_codegen = { version = "0.15.7", path = "../juniper_codegen"  }