Add drawing buttons

include/button.h

@@ -0,0 +1,16 @@
+#ifndef BUTTON_H
+#define BUTTON_H
+
+#include "window.h"
+
+#define BUTTON_WIDTH 100
+#define BUTTON_HEIGHT 40
+
+typedef struct button button_t;
+struct button {
+  rect_t rect;
+};
+
+void draw_button(const window_t *wnd, const button_t *button);
+
+#endif // !BUTTON_H