Tear down databases manually feature request

还没有人认领这个 Issue。

I think a feature that can be added to this library would be to tear down databases manually.

A use case for this would be to do this in the "tear-down" section in testing frameworks. For example, in [vitest](https://vitest.dev/) a possible implementation of this would be:

```ts
import {describe, test, beforeAll} from "vitest";
import createDb from "pg-tmp";

describe("Database test", () => {
beforeAll(async () => {
const { teardownDb } = await createDb();
// return cleanup function
return async () => {
await teardownDb();
};
});

test("specific database tests", () => {
// tests with the database.
});
});
```

This should be easy to implement using the "stop" command already implemented in `pg_tmp.sh`.

I'd be up to make a PR myself, but I figured I'd get permission first & so forth.

首先阅读 pg_tmp.sh 中现有的 stop 命令以及调用它的 Node.js API。使用 Vitest 示例作为预期用法，定义应如何从 createDb 暴露手动 teardown 函数。当调用方可以在测试清理期间调用 teardownDb，并且复用现有的数据库关闭行为时，即视为完成。

由索引模型根据 Issue 内容生成。