Folder-scoped preferences not properly supported

Folder-scoped preferences (e.g. preferences in [workspaceRoot]/.vuengine/settings.json) do not get recognized by our custom code.

We might have to explicitly factor these in as in: https://github.com/eclipse-theia/theia/blob/d7cdb85c1793ae5e4af8d05da249a2dcea606da2/packages/task/src/browser/task-configuration-manager.ts#L65