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.

test.c

@@ -99,4 +99,25 @@ main(int argc, char *argv[])
 
     free(stack);
   );
+
+  test("queue",
+    char *a = "a";
+    char *b = "b";
+    char *c = "c";
+
+    ds_queue_t *queue = ds_queue_init();
+    it("pushes an item", ds_queue_push(queue, a) == 0);
+    it("pops an item", ds_queue_pop(queue) == a);
+
+    ds_queue_push(queue, b);
+    ds_queue_push(queue, c);
+
+    it("peeks ahead", ds_queue_peek(queue, 0) == b);
+    it("peeks past the queue", ds_queue_peek(queue, INT_MAX) == NULL);
+
+    ds_queue_pop(queue);
+    ds_queue_pop(queue);
+
+    free(queue);
+  );
 }