implement load_rom and unload_rom

src/yaze.h

@@ -1,6 +1,7 @@
 #ifndef YAZE_H
 #define YAZE_H
 
+#include <cstddef>
 #include <cstdint>
 
 #ifdef __cplusplus
@@ -16,9 +17,12 @@ typedef struct Rom Rom;
 struct Rom {
   const char* filename;
   const uint8_t* data;
+  size_t size;
+  void* impl;  // yaze::app::Rom*
 };
 
 Rom load_rom(const char* filename);
+void unload_rom(Rom rom);
 
 #ifdef __cplusplus
 }