add file hashing for cache validation and provide the license to the cc0 files in the project

src/memory.h

@@ -2,8 +2,12 @@
 #define ARGON_MEMORY_H
 
 #include <stddef.h> // for size_t
+#include <gc/gc.h>
 
 // GC-managed allocations
+
+void ar_finalizer(void *obj, GC_finalization_proc fn, void *client_data,
+                  GC_finalization_proc *old_fn, void **old_client_data);
 void *ar_alloc(size_t size);
 void *ar_alloc_atomic(size_t size);
 char *ar_strdup(const char *str);