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 :)

The issue does not name files or tests. Start by locating the extension’s relative path input and autocomplete entry point, then compare its behavior with the examples in the issue. Done means typing `../` from `biz.js` shows `foo.js` and `bar.js`, and typing `./` from `bar.js` shows `foo.js`.

Written by the indexing model from the issue text.