[jextract] Conform Java objects to swift protocols

[alessdiimperio]

Delete if inappropriate. Not sure if feature requests are allowed.

I'd very much like to see the ability to conform Java classes to swift protocols.
Is there a roadmap or some way to track when/if this would be available?

[madsodgaard]

Feature requests are very welcome!

This is something I plan on tackling after async, so soon hopefully:-)