devel/asfml: New port: Ada bindings to the Simple and Fast Multimedia Library (SFML)

ASFML is an Ada semi-thick binding to SFML. The library uses Ada types,
and portable defined types, which eliminates the inclusion of Ada
interface libraries, however most of the functions are directly
imported.

Website: https://mgrojo.github.io/ASFML/

Differential Revision: https://reviews.freebsd.org/D42151