json-glib: new package

JSON-GLib is a library providing serialization and deserialization
support for the JavaScript Object Notation (JSON) format described by
RFC 4627.

https://live.gnome.org/JsonGlib/



[Peter: add license info, tweak help text]
Signed-off-by: Henrique Camargo <henrique@henriquecamargo.com>
Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>