'Couldn't start client Reason Language Server' error after building the project

```
- Install `esy` if you don't have it (`npm install -g esy`)
- Clone this repo
- `cd` to the cloned dir
- Run `esy` from the main project dir
- Run `esy symlink` to link the built artifact into the root folder at `bin.exe`
- Install the VS Code extension's dependencies `cd editor-extensions/vscode && npm i && cd ../..`
- Open this project in VS Code
```

I followed the instructions, but on the last step I get the error in the title.

Besides this, I had a bit of difficulty in building via `esy` (step 4) before I figured out that I needed to run the script as an admin on Windows 10.

Reproduce the reported setup with esy, esy symlink, the dependencies under editor-extensions/vscode, and VS Code on Windows 10. Start by checking the final VS Code launch step and the preceding build and symlink steps; done means the language client starts without the reported error.

Written by the indexing model from the issue text.