Separate vulkan code into gpu module

CMakeLists.txt

@@ -36,6 +36,10 @@ add_shaders(shaders
   frag.glsl
 )
 
-add_executable(demo demo.c)
+add_executable(demo
+  main.c
+  gpu.c
+)
 configure_target(demo)
-target_link_libraries(demo PRIVATE glfw m shaders vulkan)
+target_include_directories(demo PRIVATE "${CMAKE_CURRENT_SOURCE_DIR}")
+target_link_libraries(demo PRIVATE glfw m vulkan shaders)