Added SDL_CopyFile() and SDL_CopyStorageFile()

Fixes https://github.com/libsdl-org/SDL/issues/9553

include/SDL3/SDL_filesystem.h

@@ -327,6 +327,18 @@ extern SDL_DECLSPEC int SDLCALL SDL_RemovePath(const char *path);
  */
 extern SDL_DECLSPEC int SDLCALL SDL_RenamePath(const char *oldpath, const char *newpath);
 
+/**
+ * Copy a file.
+ *
+ * \param oldpath the old path.
+ * \param newpath the new path.
+ * \returns 0 on success or a negative error code on failure; call
+ *          SDL_GetError() for more information.
+ *
+ * \since This function is available since SDL 3.0.0.
+ */
+extern SDL_DECLSPEC int SDLCALL SDL_CopyFile(const char *oldpath, const char *newpath);
+
 /**
  * Get information about a filesystem path.
  *