add window_dims property to RenderState

include/tangerine.h

@@ -176,6 +176,7 @@ struct RenderState
 	SDLHandles handles;
 	GLContext* gl_ctx;
 	Assets assets;
+	uvec2 window_dims;
 
 	MemoryArena* rg_arena;
 	u32 num_render_groups;

src/tangerine.cpp

@@ -46,6 +46,7 @@ initRenderState(const char* window_title,
 		rs->max_render_groups = DEFAULT_RENDER_GROUP_COUNT;
 		rs->render_groups = ARENA_ALLOC(rs->rg_arena, RenderGroup,
 				DEFAULT_RENDER_GROUP_COUNT);
+		rs->window_dims = window_dims;
 		rs->handles.SDL_flags = SDL_flags;
 
 		if (!initGraphics(&rs->handles, window_title, window_dims)) {