Fixed vector_push_back() call to use memmove() instead of memcpy() - allows for region overlap

vector.h

@@ -353,7 +353,7 @@ static inline int vector_push_back(vector_t* vec, const void* element) {
     }
 
     // Copy the new element into the vector's data array
-    memcpy((char*)vec->data + (vec->size * vec->element_size), element, vec->element_size);
+    memmove((char*)vec->data + (vec->size * vec->element_size), element, vec->element_size);
     vec->size++;
 
     return 0; // Success