move windowing code into io/win

src/io/win/shader.h

@@ -0,0 +1,11 @@
+/* Copyright (c) 2025 Quinn.
+ * This is a file from the project MCA-Selector-Lite and is
+ * licensed under the MIT Licence. See the project's LICENSE file for details. */
+#pragma once
+
+#include <glad/gl.h>
+#include <stddef.h>
+#include <stdint.h>
+
+/* Initialises the (embedded) shaders onto `pipe` */
+int shader_init(GLuint pipe);