Objective-C D metal binding

[Hipreme]

Hello guys. I have been working for some time into binding Metal 
to D.
This has been quite an interesting journey and today I've reached 
a point where it is usable.
It is far from complete, but I included a lot of comments from 
Apple's documentation, and also have tested and got an entire 
Metal hello world working in D.

The API I worked on is really nice, I manually put the opIndex, 
opIndexAssign, wrapped Objective C Runtime Arrays to a strongly 
typed array in D. The main point into this binding is getting 
Metal to run on Hipreme Engine, so, I don't plan into supporting 
what I don't use. That said, I still welcome any contribution to 
make this a standard way to program using Apple's Metal.

I'll put an example folder the moment I get a dub fix for macOS.

![Metal MacOS D Hello 
World](https://user-images.githubusercontent.com/10136262/224425800-e417414e-b6be-4e92-93b4-9087b1b281a2.png)

https://code.dlang.org/packages/d-metal-binding