Use wording from Hjson website for Hjson blurb

From https://hjson.github.io.

Author: dtolnay

_src/README.md

@@ -71,8 +71,8 @@ Serde by the community.
 - [Bencode], a simple binary format used in the BitTorrent protocol.
 - [DynamoDB Items], the format used by [rusoto_dynamodb] to transfer data to
   and from DynamoDB.
-- [Hjson], a superset of JSON suitable for configuration files.
- *(deserialization only)*
+- [Hjson], a syntax extension to JSON designed around human reading and editing.
+  *(deserialization only)*
 
 [JSON]: https://github.com/serde-rs/json
 [Bincode]: https://github.com/servo/bincode