added free_shared_memory method

images.h

@@ -49,6 +49,7 @@ int image_new_shared(int width, int height, Image* img);
 void image_destroy_shared(Image img);
 
 void* create_shared_memory(size_t size);
+void  free_shared_memory(void* ptr, size_t size);
 
 #include "src/images.c"
 #include "src/bmp-format.c"

src/multithreading.c

@@ -41,3 +41,7 @@ void* create_shared_memory(size_t size) {
   // but the manpage for `mmap` explains their purpose.
   return mmap(NULL, size, protection, visibility, -1, 0);
 }
+
+void free_shared_memory(void* ptr, size_t size) {
+    munmap(ptr, size);
+}