feat(queue): introduce a queue ds, internally this is just a stack...

the only actual difference is a oneline change which makes pushing
append instead of prepend the new data.

ds.c

@@ -420,3 +420,36 @@ void
 
   return NULL;
 }
+
+ds_queue_t
+*ds_queue_init(void)
+{
+  return ds_stack_init();
+}
+
+int
+ds_queue_push(ds_queue_t *queue, void *data)
+{
+  if (queue->n == 0) {
+    queue->items = ds_sll_new_node(data);
+    queue->n++;
+    return 0;
+  }
+  int r = ds_sll_append(queue->items, data);
+  if (!r) {
+    queue->n++;
+  }
+  return r;
+}
+
+void
+*ds_queue_pop(ds_queue_t *queue)
+{
+  return ds_stack_pop((ds_stack_t *)queue);
+}
+
+void
+*ds_queue_peek(ds_queue_t *queue, unsigned x)
+{
+  return ds_stack_peek((ds_stack_t *)queue, x);
+}