Add games/idtech4a-engine

Hello! This is a port of idTech4A++ Engine, providing the game (Doom 3 /Prey / Quake 4) for OpenBSD. It is open source based on id-Software/DOOM-3: Doom 3 GPL source release and restored clients for Prey and Quake4. Uses GPL-3 licensed SDK for android versions of the game: https://github.com/glKarin/idtech4amm_doom3_sdk https://github.com/glKarin/idtech4amm_quake4_sdk https://github.com/glKarin/idtech4amm_prey_sdk since the project was originally for android. Tested on amd64 architecture on OpenBSD 7. 7 installed on real hardware: ASUS TUF GAMING B450M-PRO II AMD Ryzen 5 5600G AMD Radeon RX 580 PowerColor. (amdgpu) Works as good as on Linux. [send to ports@ 2025-19-05](https://marc.info/?l=openbsd-ports&m=174767399313776&w=2) Video: https://www.youtube.com/watch?v=KaN5iB0dEYI https://www.youtube.com/watch?v=V1f6vknHgfw https://www.youtube.com/watch?v=vLWXX1UwX9c I want to add this to the official ports tree, so please leave any feedback or suggestions on how to improve it. Thanks! Source on Github: https://github.com/glKarin/com.n0n3m4.diii4a