[Feature request] Add crJSON support to the CPP interfaces

[lrosenthol]

Describe the feature
c2pa-rs has a feature the exports the new crJSON format. Expose that option to the CPP interfaces.

Is your feature request related to a problem?
Yes, the C2PA Conformance program requires use of crJSON.

Describe alternatives you've considered
None.

[tmathern]

C FFI: contentauth/c2pa-rs#2212