Extension Development Host does not launch

[sacsar]

For context, I (too) was about to implement #59 and opened the extension itself in VSCode. When you press F5/run the extension, the Extension Development Host window never opens.

To Reproduce
Steps to reproduce the behavior:

1. Open the extension in VS Code
2. Press F5 and/or click "Run Extension"

Expected behavior
A second VSCode window (with title prefixed by [Extension Development Host]) opens. (See https://code.visualstudio.com/api/get-started/your-first-extension)

Environment:

• OS: Manjaro 22.0.0
• VS Code 1.74.2
• Version main

Additional context
The cause is using watch in the pre-launch task here: https://github.com/arrterian/nix-env-selector/blob/master/.vscode/launch.json#L19 Removing the pre-launch task and running watch in a terminal gets you as far as being able to simply restart the extension after you make a change. I'm not sure if it should be possible to "reload" in the extension development host window.

(It's also worth noting that if you run the extension in an empty window, it fails because the workspace dir is null. I assume that's known/intentional, though I did fix it. Let me know if you want a PR for that.)