Relative path input support

Hey, thank you for this great extension. I would love to see support for inputting a relative path into the field and have the files of the folder displayed. Sometimes I know the hierarchy of my files but don't know the exact name + want autocomplete.
```
a/
├── b/
├── | foo.js
├── | bar.js
├──├── c/
├──├── | biz.js
```
Inside `biz.js` one should be able to type `../` in the relative path input field and `foo.js, bar.js` should show up. Likewise given a developer is currently inside the bar.js file, typing `./` should display `foo.js`.
Let me know what you think and if I should prepare a PR :)

该 issue 未指出文件或测试。首先定位 extension 的相对路径输入和自动补全入口点，然后将其行为与 issue 中的示例进行比较。当从 `biz.js` 输入 `../` 时显示 `foo.js` 和 `bar.js`，并且从 `bar.js` 输入 `./` 时显示 `foo.js`，即视为完成。

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