array: implement array_capacity

array.c

@@ -123,3 +123,7 @@ bool array_remove(Array *arr, size_t idx) {
 size_t array_length(Array *arr) {
 	return arr->len;
 }
+
+size_t array_capacity(Array *arr) {
+	return arr->count;
+}

array.h

@@ -54,5 +54,7 @@ bool array_add_ptr(Array*, void *item);
 bool array_remove(Array*, size_t idx);
 /* return the number of elements currently stored in the array */
 size_t array_length(Array*);
+/* return the number of elements which can be stored without enlarging the array */
+size_t array_capacity(Array*);
 
 #endif