chore: 更新 .gitignore 文件

- 添加 docs 文件夹到忽略列表，以忽略 Doxygen 生成的文件
- 保持原有的忽略规则不变

lib/utils/ds/hashtable.c

@@ -52,7 +52,7 @@ static void adjust_capacity(hash_table_t* ht, int new_cap) {
     new_cap = next_power_of_two(new_cap);
     Assert(new_cap >= ht->entries.cap);
 
-    vector_header(old_entries, hash_entry_t);
+    VECTOR_HEADER(old_entries, hash_entry_t);
     old_entries.data = ht->entries.data;
     old_entries.cap = ht->entries.cap;