enable arc-mode again for obj-c++

simple shader #includes

precompiled metal shader support

improvements to shader and texture

texture support in shader

adding Texture abstraction

using hello_imgui fork

color gradient shader

add missing releases, switch to raw pointer

pimpl to limit void* casts

first working version

Update renderpass_metal.mm

Update renderpass_metal.mm

metal works if we omit the render_pass

in progress