This fixes registry endpoints to return the proper `application/json`
content-type for JSON content, also updating spec examples for that.
As per IETF specification and IANA registry [0], the `application/json`
type is a binary media, so the content-type label does not need any
text-charset selector. Additionally, the media type definition
explicitly states that it has no required nor optional parameters,
which makes the current registry headers non-compliant.
[0]: https://www.iana.org/assignments/media-types/application/json
Signed-off-by: Luca Bruno <lucab@debian.org>
Fixing typos and adding tables
Updating with testing material
Tweak after read through
Adding in Stephen's comments
Adding in Richard's comments. Fixing the broken images
closes issue #363
Another try
Signed-off-by: Mary Anthony <mary@docker.com>
