Change configurations to window scope

[apetresc]

At the moment, all leetcode-specific preferences have scope set to application, which means they can only be set in a user's global settings.json. I think it makes much more sense to have them window scoped, which basically means you can set them in your workspace's .vscode/settings.json (you can also still have base settings in your user's settings.json too; they are simply overridden by workspace-specific ones).

Most people have a single workspace/repo for their leetcode contest problems, and it makes a lot more sense to allow them to sync their vscode-leetcode settings directly in that repository, instead of asking them to pollute their system-wide settings.json for a niche extension that only really makes sense in the context of a single workspace.

(Documentation on preference scopes)