feat(layout)!: move /gl and /vk into rendering directory

as I was adding the audio module I realized it looks really ugly that
the audio-related stuff will be in its own directory and the renderer
modules will be scattered in root directory it makes way more sense this
way

Signed-off-by: Lorenzo Torres <lorenzo@sagittarius-a.org>

rendering/vk/instance.h

@@ -0,0 +1,10 @@
+/* SPDX-License-Identifier:BSD-3-Clause */
+#ifndef INSTANCE_H
+#define INSTANCE_H
+
+#include "../renderer.h"
+
+void vk_instance_init(struct renderer_context *context);
+void vk_instance_deinit(struct renderer_context *context);
+
+#endif