Add custom shader functionality

[Phlarx]

While challenging, it would be neat to have the ability to create custom shaders.

Inspiration: https://discord.com/channels/276076890714800129/424967293538402334/992398520671805530

[fentras]

Discord Message

The message is about accessing the game's pixels (framebuffer?) and then doing anything with them, be it making a screenshot, recording a video and manipulating these pixels including applying shaders (GLSL?).

I assume it could be introduced into Draw namespace. There will be two methods:

• Draw::GetPixels(vec2 size = vec2(Draw::GetWidth(), Draw::GetHeight()) will get whole screen pixels into something like MemoryBuffer object
• Draw::SetPixels(vec2 size = vec2(Draw::GetWidth(), Draw::GetHeight()) will set whole screen pixels from something like MemoryBuffer object

And one parameter:

• size can allow getting or setting only a portion of the screen

Would be interesting to see how it could work out 👀

[codecat]

I think getting a screen buffer capture should be a very different API, because it doesn't have a whole lot to do with shaders.

Post-processing shaders use the screen buffer ofcourse, but it's still kinda different, because shaders have to be written in HLSL.